Home

@Gas User`s Manual - Techware Engineering

1. Miscellaneous Functions Humidity Ratio Mole fraction of water vapor Composition Humidity Ratio GasVer Version serial no Theoretically a state point can be uniguely identified by specifying any two thermodynamic properties and the gas composition In most practical applications pressure is one of the known variables Most of the functions contained in Gas assume that pressure is one of the known variables If this is not the case one of the eguation of state functions may be used to obtain the pressure You may be familiar with gas property tables in which pressure is not one of the variables Typically the gases are treated as perfect gases in which properties such as enthalpy entropy and specific heat are not dependent upon pressure Treating the gas mixture as a perfect gas produces only rough approximations of the actual properties The perfect gas approximations are reasonable at low pressures but increase in error as the pressure is increased The formulations used in Gas are based on real gas properties and include the effects of pressure and the mixing of the gases A function GasPTXW is provided to obtain the saturated humidity ratio for a known pressure and temperature The Dry Bulb Temperature at saturation is synonymous with the Dew Point Temperature Therefore this function can be used with a pressure and the Dew Point Temperature to obtain the moisture content The inverse of this f
2. 3 or SIF 4 or SIK 5 or MET 6 or METF Return Value Description specific entropy is the specific entropy per mass of water in units consistent with the selected unit set and referenced to saturated liquid water at the triple point Examples P 14 696 psia T 100 deg F GasCondPTS 14 696 100 0 0 1296 Btu F lbm Gas for Windows Version 3 2 User s Manual Appendix I Gas Detailed Function Listing Page 72 GasVer GasVer returns the Gas version and serial number Arguments None Return Value Description Version and Serial Number is a floating point number whose integer part represents the major version number of the DLL The first digit to the right of the decimal point represents the minor version number The remaining digits represent the serial number Examples GasVer 3 035999 The version number is 3 0 The serial number is 35999 Gas for Windows Version 3 2 User s Manual Appendix II Gas Error Codes Page 73 APPENDIX Il GAS ERROR CODES If an error is encountered by an Gas function during calculation of a gas property the function returns a negative value 1000 or lower This Appendix presents the error numbers together with an explanation of each possible error condition The header file GASERR H defines mnemonic constants for the error codes The mnemonics are listed below also The error codes listed below are accessible only from Windows programming languages s
3. To load the add in after it is registered click on the path name that has the 123GAS 12A file A check mark will appear to the left of the path name indicating that the add in is selected Press the Done push button to complete the task Gas for Windows Version 3 2 User s Manual Chapter 2 Using the Gas Property Functions Page 9 Thereafter each time you start 1 2 3 the functions will be loaded automatically If you wish to unload the functions use the Add In manager to deselect the add in From there forward the 123GAS 12A add in will not load until you select it again using the Add In Manager as described above but it should be unnecessary to go through the registration process again Once the add in is loaded the gas property functions can be used in any cell formula by typing the function name in the same ways as 1 2 3 s built in functions If you need help use the 1 2 3 Help menu and select the Gas Help item This will launch an interactive help window which provides information regarding the functions and their usage When the add in is loaded the gas property functions are available in the same ways as 1 2 3 s built in functions That is they can be typed directly into cell formulas Generally you can use any of the functions listed in section 2 2 in any cell formula simply by prefixing the function name with an character The Gas package contains a sample 1 2 3 spreadsheet file named EXAMPLE 123 which makes sev
4. Pressure Heat Flow if you know the pressure and heat added or removed If you are measuring performance on an existing device you will need to know the exiting gas temperature or enthalpy Check either of the Pressure Enthalpy or Pressure Temperature buttons as required The two variables you have chosen will have their value fields enabled all others will be grayed Enter the appropriate values and click the Compute button The Gas Flow In column displays the state point properties entering the equipment which were copied from the Active Point in the main screen window The Total Flow Out box has three columns that display the state point properties at the end of the expansion The first column identifies the thermodynamic properties for the mixture of moist gas and liquid water exiting the equipment The second column displays the thermodynamic properties for the moist gas exiting and the third column shows the properties for the liquid water if any condensation occurs The units displayed are those currently in use on DeskTop Gas s main Gas for Windows Version 3 2 User s Manual Chapter 3 Using DeskTop Gas Calculator Page 19 window If you wish to use different units you should select those units on the main window before opening the Heating Cooling tool Below the state point properties you will find the heat added based on the entering gas flow rate that you entered The units for these results will
5. Xnas Xoz Xan Xco2 XH20 unit set Return Value specific volume Description is a value representing the absolute total pressure of the gas in units consistent with the selected unit set is a value representing the dry bulb temperature of the gas in units consistent with the selected unit set the gas composition N2 O2 Ar CO2 H20 of the gas Xy2 Xo2 Xar and Xco2 are entered as mole fractions of the dry gas with Xuso entered as a humidity ratio All of the five arguments must be entered in order even if any are zero If 32 is added to the unit set all X values are entered as mole fractions of the wet gas If 64 is added to the unit set mass fractions are substituted wherever mole fractions are required 0 or ENG 1 or SI 2 or EngG 3 or SIF 4 or SIK 5 or MET 6 or METF Description _ _ _ _ is the specific volume per mass of dry gas in units consistent with the selected unit set If 16 is added to the unit set output is per mass of wet gas Examples P 14 696 psia T 100 deg F N2 0 740285 O2 0 198589 Ar 0 008855 CO2 0 000298 H2O 0 051973 GasPTXV 14 696 100 0 740285 0 198589 0 008855 0 000298 0 051973 48 14 387 ft Ibm of wet gas Gas for Windows Version 3 2 User s Manual Appendix Gas Detailed Function Listing Page 51 GasPVXT GasPVXT pressure volume Xn2 Xo2 Xan Xco2 X20 unit set returns the temperature of the moi
6. 500 0 001 0 003 0 009 NI Ol ol E All GC l Gl CH EE ES 0 170 0 033 0 056 0 038 0 022 0 038 1 38 0 50 1 40 EE Notes Questionable reference data Chapter 5 Speed and Accuracy Page 44 Gas for Windows Version 3 2 User s Manual Chapter 5 Speed and Accuracy Page 45 COMPARISON OF RESULTS WITH HYLAND amp WEXLER 8 SATURATED HUMIDITY RATIO OF MOIST AIR kg of Water Vapor kg of Dry Air TABLE 2 Pressure 1 bar Temp deg C Hyland amp Wexler a aa 0 00384 00834 00834 o 1 4833 1 4835 1 4833 TABLE 26 Pressure 5 bar Po Les Sooo aan a IL em Lues ue TABLE 27 Pressure 10 bar o Lues Lass 0 00005 o ooe Laser oue TABLE 28 Pressure 50 bar Lamera C o Le Les 0 00009 rn nor Le oos ml nem Las oors e Les Luss 0 0087 Om ore ore omas res onse ore ore RSR 0 3306 0 3263 0 3263 Gas for Windows Version 3 2 User s Manual Chapter 5 Speed and Accuracy Temp COMPARISON OF RESULTS WITH HYLAND amp WEXLER 8 SPECIFIC VOLUME OF SATURATED MOIST AIR m kg of Dry Air TABLE 29 Pressure 1 bar os TABLE 30 Pressure 5 bar SCH SCH Temp TABLE 31 Pressure 10 bar ESCH ae CR 0 James oorssee E a oo21a10 000050 01021302 o 000008 0 021301 0 000008 SCH e m SCH d TABLE 32 Pressure 50 bar Gas for Windows Version 3 2 User s Manual Page 46
7. Chapter 5 Speed and Accuracy Page 47 The differences in saturated humidity ratios between Air or Gas and Hyland amp Wexler can be attributed mostly to the equations used to calculate the pressure of saturated vapor over liquid water Air and Gas use the latest equations provided by IAPWS 7 In the following comparisons the properties calculated by Air and Gas use the saturated humidity ratio as calculated by Hyland amp Wexler in order to show a comparison based on the same composition Gas for Windows Version 3 2 User s Manual Chapter 5 Speed and Accuracy Page 48 6 REFERENCES Tables of Thermal Properties of Gases NBS Circular 564 1955 Vasserman A A Kazavchinskii Ya Z and Rabinovich V A Thermophysical Properties of Air and Air Components Nauka Press Moscow 1966 English translation by Israel Program for Scientific Translations Ltd available from NTIS Springfield Va 1971 as TT70 50095 Rabinovich V A Beketov V G Moist Gases Thermodynamic Properties Begell House Inc New York 1995 Hirschfelder J O Curtiss C F and Bird R B Molecular Theory of Liquids and Gases John Wiley and Sons 1954 Mangum B W and Furukawa G T Guidelines for Realizing the International Temperature Scale of 1990 ITS 90 NIST Technical Note 1265 1990 6 Thermodynamic and Transport Properties of Steam ASME New York NY 1993 7 The IAPWS Formulation 1995 for the The
8. ERR_PHIGH 3000 Pressure Too High Gas will accept a maximum pressure of 50 bar ERR PLOW 3100 Pressure Too Low Gas will accept a minimum pressure of 1 Pascal ERR_VOLLOW 4100 Volume Too Low Specific volume is below the minimum allowed by Gas ERR_WHIGH 7000 Humidity Ratio Too High The humidity ratio specified is above the saturated humidity ratio for the gas pressure and temperature ERR WLOW 7100 Humidity Ratio Too Low The humidity ratio specified is below 0 ERR HHIGH 9000 Enthalpy Too High The enthalpy specified represents a state point above the Gas pressure and temperature limits ERR HLOW 9100 Enthalpy Too Low The enthalpy specified represents a state point below the Gas pressure and temperature limits ERR SHIGH 9200 Entropy Too High The entropy specified represents a state point outside the Gas pressure and temperature limits ERR SLOW 9300 Entropy Too Low The entropy specified represents a state point outside the Gas pressure and temperature limits ERR INTERNAL 9999 Internal Error One of the iteration schemes has failed to converge Contact Techware for support Gas for Windows Version 3 2 User s Manual
9. 000298 H20 0 051973 GasPSXT 14 696 0 1154 0 740285 0 198589 0 008855 0 000298 0 051973 48 100 deg F Gas for Windows Version 3 2 User s Manual Appendix I Gas Detailed Function Listing Page 67 GasPTXL GasPTXL pressure temperature Xn2 Xo2 Xan Xco2 X20 unit set returns the mass of water condensed per mass of gas Arguments Description pressure is a value representing the absolute total pressure of the gas in units consistent with the selected unit set temperature is a value representing the dry bulb temperature of the gas in units consistent with the selected unit set Xnz Xoz Xan Xco2 XH20 the gas composition N2 O2 Ar CO2 H20 of the gas Zus Kos Xar and Xco2 are entered as mole fractions of the dry gas with X20 entered as a humidity ratio All of the five arguments must be entered in order even if any are zero If 32 is added to the unit set all X values are entered as mole fractions of the wet gas If 64 is added to the unit set mass fractions are substituted wherever mole fractions are required unit set 0 or ENG 1 or SI 2 or EngG 3 or SIF 4 or SIK 5 or MET 6 or METF Return Value Description water condensed is the mass of water condensed per mass of dry gas in units consistent with the selected unit set and ASHRAE reference point If 16 is added to the unit set output is per mass of wet gas If temperature is above dew point the function returns 0 Exa
10. 2 2 2 Basic Unit Sets Input to all the functions and all results can be in any of the available unit sets Gas lets the user select the desired unit set with each function call through the use of an extra function argument the unit set parameter The unit set parameter selects basic units Eng SI etc and optional unit set modifiers The gas property functions within the function library contain the required conversion factors When calling gas property functions from Visual Basic or any other Windows programming language the unit set parameter is required and must be an integer value Additional flexibility in entering the unit set parameter is available when using the gas property add in functions from Excel or 1 2 3 The spreadsheet add ins allow the unit set parameter to be entered either as a character string or an integer value Acceptable character strings are listed in the row labeled Unit Set Name in the table below Modifiers can also be appended to these strings as described later in this section For most users the character string method is preferable because the characters representing the unit sets and their options are mnemonic For Mathcad the unit set can only be entered as a number however you can achieve the same effect by defining mnemonics for the base unit sets and the options right on your Mathcad worksheet The table below summarizes the units used for each unit set er a e Customary Gauge Formal UnitSe
11. GAS USER S MANUAL VERSION 3 2 COPYRIGHT NOTICE The Gas software and manual are copyrighted and licensed for use by one user per copy purchased This manual and the software described in it are copyrighted with all rights reserved Under the copyright laws this manual or the software may not be copied in whole or part without written consent of Techware Engineering Applications Inc Techware Engineering Applications Inc grants permission to the purchaser to make a limited number of copies of the add in for backup purposes only provided that the copies are not in use at the same time as the original Additional reproduction of the software is a violation of copyright law Violators will be prosecuted to the fullest extent of the law Copyright 1997 2002 2009 Techware Engineering Applications Inc All rights reserved TRADEMARKS The following trademarks are used throughout this manual They are registered trademarks of the companies shown Lotus and 1 2 3 are trademarks of Lotus Development Corporation Excel Windows Visual C C and Visual BASIC are trademarks of the Microsoft Corporation Mathcad is a trademark of MathSoft Inc 1 INTRODUETION 22252 ee Nee n es ed ee DE ee 1 1 1 TN cc cra ee ee rd cre ad tral Saal eelere 1 1 2 WV IVES E 2 USING THE GAS PROPERTY FUNCTIONS eee eee 3 2 1 General le e nee D 3 2 2 Description of Gas FUNCUONS 2 220 202 cena ena A eae Aeneas 3 2 2 1 Vald Operatin
12. Gas functions is copied to a Programming folder in the Gas program folder if the Programming option was selected during installation With each TGAS32 function call your code should check to ensure that the values returned are greater than 1000 Return values of less than 1000 indicate error conditions See the Appendix for a listing of error codes and their meanings 2 7 USING GAS FROM C C WINDOWS PROGRAMMING LANGUAGES The gas property functions in TGAS32 DLL can also be called from within C C programs compiled to run under Windows Prototypes for all functions are provided in the file named GASPROTO H All files needed to support your programming applications can be found in the Programming folder if you choose to install programming support during installation You may also find it convenient to include the file named GASERR H It defines mnemonic Gas for Windows Version 3 2 User s Manual Chapter 2 Using the Gas Property Functions Page 11 constants for the various error values returned by the gas functions The compiled code should also be linked with the import library named TGAS32 LIB With each gas property function call your code should check to ensure that the values returned are greater than 1000 Return values of 1000 or smaller indicate error conditions See the Appendix for a listing of error codes and their meanings 2 8 VERSION AND SERIAL NUMBER There may be new releases of Gas
13. Techware s WinSteam add in Gas for Windows Version 3 2 User s Manual Chapter 1 Introduction Page 2 The Gas package supports 32 bit applications running under Windows 95 98 NT XP and Windows 2000 The Setup program will try to detect which applications are installed on your system and offer appropriate options for installation The Setup program and the installation instructions contained in the Gas package guide you through installing the files you ll need for the applications you expect to use Example files to help you get started are also provided 1 2 WHAT S NEW Gas 3 2 does not install the help shortcut on the toolbar when using Excel 2007 or later in order to operate more reliably Gas 3 0 has added many new features over the previous version Gas 2 0 These include the following Extends the temperature range upwards from 1300 K 1880 F to 2000 K 3140 F and downward from 273 15 K 32 F to 180 K 135 67 F Adds transport property functions GasPTXM which calculates dynamic viscosity given pressure temperature and gas composition GasPTXK which calculates thermal conductivity given pressure temperature gas composition The gas property calculator now called DeskTop Gas has been enhanced to include many new features to make it even more powerful Adds five new unit sets EngG which uses psig for pressure instead of psia SIF which uses the formal SI units MPa for
14. The functions are valid over a temperature range from 180 K 136 F to 2000 K 3140 F and at pressures up to 50 bar 725 psia Gas can be used to calculate the thermodynamic and transport properties of moist air by calling the functions using the composition of standard air In some cases when dealing with psychrometric properties of air such as relative humidity wet bulb temperature or degree of saturation it may be necessary to use Techware s Air add in which includes functions to handle these parameters The two packages use similar equations except that the Air program mixes two gases dry air plus moisture while the Gas product mixes five discrete gases Nonetheless the values returned by the Gas functions when using a mixture composition corresponding to standard dry air agree quite well with those returned by the Air functions For this reason the functions from the two programs can be used together as long as you select consistent unit sets Included also in Gas are functions that calculate the saturated vapor pressure of water and the enthalpy and entropy of compressed water These functions are useful in calculations involving the removal of moisture from gas streams The saturated vapor functions and the enthalpy and entropy property values for compressed liquid water are based on the IAPWS IF97 formulations used to develop the ASME steam tables For a complete set of thermodynamic properties for water and steam use
15. and the second cross virial coefficient of the mixture can be expressed as B Buty T AE Similarly the third virial coefficients can be expressed as R 3 3 3 3 CANNON CoooXo C aaaXa Ceke 2 wwoXo C yyaX a LC vue ke IG 2 oon n CoosX 4 Cooc c he T 2 con y CecoXo Ceca e We T c c C seg 3 C c 2 aanXy C 10X0 C aacXc a Es CyocXy XoXc j CyscXnX ate CogcXoX ac and 2 2 2 2 Cw YN CoowXo C aap Xa CocwXe 2 Low a CyswX wX4 CycwXyXc 1 xy RR Cacr Yak c CycwX Ate and LC Ber CowwXo T C awk T Capel x where the subscripts N O A and C refer to N2 O2 Ar and CO respectively Assuming that the condensed phase is pure water the value of Xeq can be found by equating the chemical potential of pure condensed water with the chemical potential of its vapor in the Gas for Windows Version 3 2 User s Manual Chapter 4 Theoretical Basis of Gas Functions Page 23 gas solution Since the equations describing chemical potentials are non linear and difficult to analyze phase equilibrium is often described in terms of a thermodynamic function called fugacity The equality of chemical potentials can be replaced by equating the logarithms of the fugacity of pure condensed water with that of its vapor in the gas mixture solution The equation of solubility based on this concept is derived by Rabinovich 3 and can be expressed as follows Xap de ps
16. eg K deg K Avg Max Avg Max Avg Max Error Error Error Error Error Error 180 Gen 0 049 0 376 0 082 0 529 0 075 0 199 Gas for Windows Version 3 2 User s Manual Chapter 5 Speed and Accuracy Page 37 COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 9 ENTHALPY OF CARBON DIOXIDE Range deg K deg K Avg Max Avg Max Avg Max SEHE A NBS data not available COMPARISON OF RESULTS WITH ASME 6 DATA TABLE 10 ENTHALPY OF WATER VAPOR Temperature Pressure Range deg K deg K Avg Max Avg Max Avg Max Error Error Error Error Error Error Gas for Windows Version 3 2 User s Manual Chapter 5 Speed and Accuracy COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 11 ENTROPY OF NITROGEN Temperature Pressure Range From deg K 180 260 10 60 410 10 10 710 810 1500 i e e as ee Error Error Error Error Error Error COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 12 ENTROPY OF OXYGEN Temperature Pressure Range deg K Avg Max Avg Max Avg Max Error Error Error Error Error Error 600 bo kor bank bos ber Gas for Windows Version 3 2 User s Manual Page 38 Chapter 5 Speed and Accuracy Page 39 COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 13 ENTROPY OF ARGON Range fom fo tam oam an deg K deg K Avg Max Avg Max Avg Max ee e reo bar kees Ka Kas Krez Kis hoe 260 soo 0 000 1 1 bes H 1 non boer kee 1 bes ooie loose beer THH 1 beer beer bere 10 son ko 1 bas E 10 r
17. for Windows Version 3 2 User s Manual Appendix I Gas Detailed Function Listing Page 54 GasPTXS GasPTXS pressure temperature Xy2 Xo2 Xar Xco2 X20 unit set returns the specific entropy of the moist gas Arguments pressure temperature Xna Xoz Xan Xcoz XH20 unit set Return Value specific entropy Examples Description is a value representing the absolute total pressure of the gas in units consistent with the selected unit set is a value representing the dry bulb temperature of the gas in units consistent with the selected unit set the gas composition N2 O2 Ar CO2 H20 of the gas Zus Kos Xar and Xco2 are entered as mole fractions of the dry gas with Xuso entered as a humidity ratio All of the five arguments must be entered in order even if any are zero If 32 is added to the unit set all X values are entered as mole fractions of the wet gas If 64 is added to the unit set mass fractions are substituted wherever mole fractions are required 0 or ENG 1 or SI 2 or EngG 3 or SIF 4 or SIK 5 or MET 6 or METF Description is the specific entropy per mass of dry gas in units consistent with the selected unit set and ASHRAE reference point If 16 is added to the unit set output is per mass of wet gas If 8 is added to the unit set entropy is referenced to absolute zero temperature Examples gt RR Ek PES Ser P 14 696 psia T 100 deg F N2 0 74028
18. for Windows Version 3 2 User s Manual Chapter 5 Speed and Accuracy Page 43 COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 21 COMPRESSIBILITY OF DRY AIR Temperature Pressure Range deg K Avg Max Avg Max Avg Max Avg Max c 8 6 Sol Ga olojo CH 0 500 g COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 22 ENTHALPY OF DRY AIR Temperature Pressure Range eg K deg K Avg Max Avg Max Avg Max Error Error Error Error Error Error 250 0 004 0 016 0 031 10 119 0 125 0 262 300 0 001 0 002 0 004 0 009 0 037 0 070 350 fo 001 0 003 0 005 0 008 0 007 10 011 400 0 002 0 005 0 008 0 009 0 006 0 009 500 fo 001 10 002 0 005 0 007 0 005 0 011 eoo fo 001 0 002 0 001 0 003 0 005 0 007 700 fo 001 0 002 0 001 0 001 0 007 0 008 180 260 e 260 mo f 510 610 RER zeck E EFFE d 180 260 310 360 410 510 610 710 810 1500 Gas for Windows Version 3 2 User s Manual COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 23 ENTROPY OF DRY AIR Range deg K deg K Avg Max Avg Max Avg Max aad ee COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 24 SPECIFIC HEAT OF DRY AIR Temperature Pressure Range eg K deg K Avg Max Max Avg Max Error Error Error Error Error 250 J0 036 0 098 0 352 1 026 1 046 3 162 H Q ND CO CH 60 10 E 350 0 005 0 007 0 020 de 60 400 G ng J0 002 0 004 10
19. is for temperature and c1 through g1 are for the gas composition The last argument selects the units set and any options The Gas package includes a sample Excel spreadsheet file named EXAMPLE XLW which illustrates use of the gas property functions You can find this file in a Samples folder in the Gas program folder Since the Gas property functions make many floating point calculations they can add to a spreadsheet s recalculation time You may find it desirable to set the spreadsheet to manual recalculation rather than automatic 2 4 USING GAS FROM 1 2 3 Gas works with 32 bit versions of 1 2 3 including 1 2 3 97 and 1 2 3 Millennium You must load the add in file named 123GAS 12A to access the gas property functions from 1 2 3 When the add in is loaded into memory it establishes links between 1 2 3 and the Gas dynamic link library Use the File Add Ins Manage Add ins menu selections to start the Add In Manager Before you can use the Gas add in for the first time you must register the add in by pressing the Add In Manager s Register push button If installed using the default values the file 123GAS 12A should be in the LOTUS 123 ADDINS directory and will be shown in the Register Add Ins window If you installed the file elsewhere you will have to use the Look in window to search for the file When you have located the 123GAS 12A file select it and press the Open push button The add in is now registered
20. it is probably more convenient to express the composition on a wet basis In this case all of the gas components including H20 are expressed as mole fractions This option is enabled by appending C to the to the unit set name For example if you are working in English units you would enter the unit set as EngC If you prefer to express the gas composition in terms of mass fractions instead of mole fractions you may do so by appending M to the unit set name For example the unit set EngM would require the gas composition for N2 O2 Ar and CO to be entered as mole fractions and HO as a humidity ratio The unit set EngCM would require all five gas components to be entered as mass fractions If you are using the numerical designation for unit sets you can select the C option by adding 32 to the unit set number or the M option by adding 64 to the unit set number 2 2 4 Wet or Dry Basis All mass dependent properties specific volume enthalpy entropy specific heat and viscosity can be expressed on either a dry or wet basis The default for all basic unit sets expresses the properties per mass of dry gas This is consistent with ASHRAE conventions and is quite useful when dealing with processes that involve evaporation or condensation of water vapor If you have chosen to express the gas composition on a wet basis selected the C unit set modifier you probably want to express the property value
21. on a wet basis as well You can accomplish this by adding the letter W to the unit set name or adding 16 to the unit set number In this case the properties will be expressed per total mass of the wet gas including the water vapor Some of the functions the inverse functions take per mass properties as inputs Remember that the choice of wet or dry basis affects the property whether it is used as an input or output parameter 2 2 5 Reference Conditions Enthalpy and entropy values are always expressed relative to particular reference conditions Many people forget that the values of enthalpy and entropy that are found in published tables are not absolute values but instead are relative to particular reference conditions Engineering calculations always deal with enthalpy or entropy differences typically between in flowing and out flowing streams For this reason it does not matter what you select as the reference conditions as long as you use them consistently Gas allows you to select reference Gas for Windows Version 3 2 User s Manual Page 6 Chapter 2 Using the Gas Property Functions Page 7 conditions consistent with ASHRAE or an alternate set of conditions based on absolute zero temperature In SI units ASHRAE uses a reference condition of 0 C and one atmosphere of pressure for dry air For water vapor ASHRAE uses a reference condition of liquid water at the triple point temperature of 0 01 C In English uni
22. pressure instead of bar and K for temperature instead of C SIK which uses kPa instead of bar for pressure MET which uses the calorie instead of the joule for energy and METF which uses kg cm for pressure Gas for Windows Version 3 2 User s Manual Chapter 2 Using the Gas Property Functions Page 3 2 USING THE GAS PROPERTY FUNCTIONS 2 1 GENERAL INFORMATION All applications using the gas property functions use the same set of functions In most applications the functions are called by name In DeskTop Gas the appropriate functions are called automatically according to your on screen selections Each user of spreadsheets or programs you write using the gas property functions must have his own copy of Gas Any program calling the functions must access the dynamic link library at run time Since this file will be called by many applications it must be installed on the computer in either the Windows directory or preferably in the Windows System directory Normally the installation program will set this up for you automatically In Excel 1 2 3 Mathcad Visual BASIC and your own Windows programs the functions provided by Gas can be used within equations just like each application s built in math functions The functions can even be nested Each function returns a single floating point result The functions require several inputs to identify the state point the gas composition and the unit set Subsequent s
23. sess ces cect aes sh EE ch eh ah EEN ah ae ae ea N 28 9 SPEED AND ASGGURAC Va ME Er ee see oe ER oe ie ed en Ge de bee 31 5 1 SEILER SN 5 2 Accuracy Eege deed dee Ee EE GE De EE Ge EES 31 6 FREE E e 48 APPENDIX DETAILED FUNCTION LISTING AAA 49 APPENDIX Il GAS ERROR CODES an ee 73 Chapter 1 Introduction Page 1 1 INTRODUCTION Gas is a software product that provides thermodynamic and transport properties for mixtures of moist gases through functions contained in a Windows Dynamic Link Library DLL The Gas package includes DeskTop Gas an interactive gas property calculator and various add ins which allow the functions to be used as if they were built in to 1 2 3 for Windows Microsoft Excel and Mathcad Programmers can call the functions in the DLL directly from many Windows programming languages such as Microsoft s Visual Basic Visual C and Access 1 1 OVERVIEW The current library includes the following gases nitrogen N2 oxygen O2 argon Ar carbon dioxide CO2 and water vapor H20 The thermodynamic property functions are calculated for mixtures of all five gases using an accurate third order virial equation of state See the theory and accuracy section of the HTML version of the User s Manual for an explanation of how Techware developed the equation of state These five gases account for 99 997 of the volumetric composition of standard air and also account for better than 99 9 of most combustion gases
24. to add features or to support new applications Each new release of Gas will have a version number Every copy of Gas sold also has a unique serial number You can identify the version of the DLL and serial number of your copy by using the GasVer function which takes no arguments In Excel an empty pair of parentheses is needed In 1 2 3 no parentheses are needed The GasVer function returns a floating point number containing the information e g 3 012345 The first two digits indicate the DLL version number The next five digits make up your copy s serial number The serial number also can be found by selecting About on the Help menu of DeskTop Gas Gas for Windows Version 3 2 User s Manual Chapter 3 Using DeskTop Gas Calculator Page 12 3 USING DESKTOP GAS CALCULATOR 3 1 OVERVIEW DeskTop Gas is a Windows application which calculates the thermodynamic and transport properties of a mixture of moist gases It can be used as an interactive replacement for gas property tables but does much more than that It automatically calculates all unknown properties when a state point is defined by known properties The program is flexible and designed to minimize keystrokes for common calculations DeskTop Gas allows you to enter any number of state points label them and store the collection of points for later reference You can print a table of stored points or copy them to the clipboard and paste them into your favorite spreadsheet
25. 2 or EngG 3 or SIF 4 or SIK 5 or MET 6 or METF Description is the specific entropy per mass of dry gas in units consistent with the selected unit set and ASHRAE reference point If 16 is added to the unit set output is per mass of wet gas If 8 is added to the unit set entropy is referenced to absolute zero temperature LU ET ss m m sw ER ER Den Eg ek P 14 696 psia T 100 deg F N2 0 740285 O2 0 198589 Ar 0 008855 CO2 0 000298 H20 0 051973 GasPTXSs 14 696 100 0 740285 0 198589 0 008855 0 000298 0 051973 48 0 1319 Btu F lbm of wet gas Gas for Windows Version 3 2 User s Manual Appendix Gas Detailed Function Listing Page 57 GasPTXC GasPTXC pressure temperature X va Xo2 Xar Xco2 Xn2o unit set returns the specific heat of the moist gas Arguments pressure temperature Xna Xoz Xan Xcoz XH20 unit set Return Value specific heat Examples Description is a value representing the absolute total pressure of the gas in units consistent with the selected unit set is a value representing the dry bulb temperature of the gas in units consistent with the selected unit set the gas composition N2 O2 Ar CO2 H20 of the gas Zus Kos Xar and Xco2 are entered as mole fractions of the dry gas with Xuso entered as a humidity ratio All of the five arguments must be entered in order even if any are zero If 32 is added to the unit set all X values are ent
26. 3 or SIF 4 or SIK 5 or MET 6 or METF Description is a value representing the ratio of the mass of water vapor in the gas to the mass of all the other gas components Examples N2 0 740285 O2 0 198589 Ar 0 008855 CO2 0 000298 H20 0 051973 GasXW 0 740285 0 198589 0 008855 0 000298 0 051973 32 0 3409 mass of water per mass of dry gas Gas for Windows Version 3 2 User s Manual Appendix Gas Detailed Function Listing Page 63 GasWX GasWX Xn2 Xo2 Xan Xco2 X20 unit set returns the mole fraction of water vapor Arguments Description XN2 Xoz Xan Xco2 XH20 the gas composition N2 O2 Ar CO2 H20 of the gas Zus Kos Xar and Xco2 are entered as mole fractions of the dry gas with X20 entered as a humidity ratio All of the five arguments must be entered in order even if any are zero If 32 is added to the unit set all X values are entered as mole fractions of the wet gas If 64 is added to the unit set mass fractions are substituted wherever mole fractions are required unit set 0 or ENG 1 or SI 2 or EngG 3 or SIF 4 or SIK 5 or MET 6 or METF Return Value Description water vapor mole fraction is a value representing mole fraction of water vapor in the gas Examples N2 0 740285 O2 0 198589 Ar 0 008855 CO2 0 000298 W 0 0310 GasWX 0 740285 0 198589 0 008855 0 000298 0 0309 0 0 05197 mass of water per mass of dry gas G
27. 5 O2 0 198589 Ar 0 008855 CO2 0 000298 H20 0 051973 GasPTXS 14 696 100 0 740285 0 198589 0 008855 0 000298 0 051973 48 0 1154 Btu F lbm of wet gas Gas for Windows Version 3 2 User s Manual Appendix Gas Detailed Function Listing Page 55 GasPTXHs GasPTXHs pressure temperature Xy2 Xo2 Xar Xco2 Xuzo unit set returns the saturated specific enthalpy of the moist gas Arguments pressure temperature MNS Xoz Xan Xcoz XH20 unit set Return Value specific enthalpy of gas saturated with water vapor Examples Description is a value representing the absolute total pressure of the gas in units consistent with the selected unit set is a value representing the dry bulb temperature of the gas in units consistent with the selected unit set the gas composition N2 O2 Ar CO2 H20 of the gas Zus Kos Xar and Xco2 are entered as mole fractions of the dry gas with Xuso entered as a humidity ratio All of the five arguments must be entered in order even if any are zero If 32 is added to the unit set all X values are entered as mole fractions of the wet gas If 64 is added to the unit set mass fractions are substituted wherever mole fractions are required 0 or ENG 1 or SI 2 or EngG 3 or SIF 4 or SIK 5 or MET 6 or METF Description is the specific enthalpy per mass of dry gas in units consistent with the selected unit set and ASHRAE reference point
28. Box re evaluate it Note that the box retains the last number or expression entered even after a compute command is issued As a result the value in the box will not reflect the value of the recalled expression if a compute command has altered the value You may use the Cut Copy and Paste commands on the Edit menu or the toolbar to exchange numeric data between DeskTop Gas IO Boxes and any other application that supports the clipboard If you start entering data in an IO Box and wish to go back to the original data you may use the Undo command on the Ed menu However once the IO Box loses the focus the Undo command is no longer available 3 4 UNIT SELECTION DeskTop Gas allows you to use any combination of units for input and output properties The units for each property can be set independently by using its associated combo box To change a unit select its combo box and scroll through the list of available units using either the Gas for Windows Version 3 2 User s Manual Chapter 3 Using DeskTop Gas Calculator Page 15 keyboard cursor arrows or the mouse Whenever a new unit is selected the program converts the values displayed for that property to the new units Therefore when entering data you should first select the units and then key in the input values Otherwise the values will be converted to the new units and you will have to re enter them The first time the program is started the properties will be di
29. If 16 is added to the unit set output is per mass of wet gas If 8 is added to the unit set enthalpy is referenced to absolute zero temperature LU ET Ss EER u EER EE P 14 696 psia T 100 deg F N2 0 740285 O2 0 198589 Ar 0 008855 CO2 0 000298 H20 0 051973 GasPTXHs 14 696 100 0 740285 0 198589 0 008855 0 000298 0 051973 68 806 Btu lbm of wet gas Gas for Windows Version 3 2 User s Manual Appendix Gas Detailed Function Listing Page 56 GasPTXSs GasPTXSs pressure temperature XN2 Xo2 Xar Xco2z Xuzo unit set returns the saturated specific entropy of the moist gas Arguments pressure temperature MNS Xoz Xan Xcoz XH20 unit set Return Value specific entropy of gas saturated with water vapor Examples Description is a value representing the absolute total pressure of the gas in units consistent with the selected unit set is a value representing the dry bulb temperature of the gas in units consistent with the selected unit set the gas composition N2 O2 Ar CO2 H20 of the gas Zus Kos Xar and Xco2 are entered as mole fractions of the dry gas with Xuso entered as a humidity ratio All of the five arguments must be entered in order even if any are zero If 32 is added to the unit set all X values are entered as mole fractions of the wet gas If 64 is added to the unit set mass fractions are substituted wherever mole fractions are required 0 or ENG 1 or SI
30. Ir 28 BE In SS In oT T ES lL Vana AP S avi E 2 3 E GES C pew Je et ggw gww where B C z 1 the compressibility of the gas mixture or the water vapor as required U U p saturation pressure of water vapor at temperature T v the volume of the condensed water wcond The solubility equation can be solved for Xeq by iteration For an ideal solution Xegidear is equal to the ratio of the vapor pressure of the pure water to the total pressure of the mixture The ratio Of Xeg Xegideal is Called the enhancement factor or excess solubility and has a value greater than 1 The value of Xeq is used to find the dew point temperature of a gas mixture to determine the amount of condensation that occurs in a cooling process and to verify that the value of x input by the user does not exceed Xeg The thermodynamic properties enthalpy entropy and specific heat at constant pressure can be determined from knowledge of the properties in the ideal gas state and the virial coefficients The molar enthalpy of a moist gas mixture hm can be described by the equation hy Xy he hy xo hg thy x ay thi ETER h a RT AB 1 oni Zell hy S 2 E o v where h ideal gas molar enthalpy for gas i h constant to adjust reference state for gas i Gas for Windows Version 3 2 User s Manual Chapter 4 Theoretical Basis of Gas Functions Page 24 The molar entropy of the moist gas mixture sm
31. NS Il A Thermal conductivity of water vapor at the specified temperature PW EMM M OI gw A G SW and C 1989 1E 7 Bo function of reduced temperature To correct for pressure we use the Stiel and Thodos modification as described in Reid Prausnitz and Poling 9 Gas for Windows Version 3 2 User s Manual Chapter 5 Speed and Accuracy Page 31 5 SPEED AND ACCURACY 5 1 SPEED OF CALCULATIONS This section addresses the Gas calculation speed as measured within Microsoft Excel Performance within other applications is similar The time required to recalculate a spreadsheet is a function of many features of the computer system hardware and the nature of the spreadsheet Since the supported spreadsheets use double precision math exclusively calculation time is sensitive to the number and complexity of numerical equations used The time required to perform the calculations also varies depending on the specific functions Some calculations are more complex than others Some require iterations The simplest functions run the fastest while those that are more complex and require iterations run slower The table below lists times required to calculate some typical Gas functions from Microsoft Excel Calculation Time GasPVXT 0 0002 GasPTXV 0 0002 GasPTXH 0 0002 GasPHXT 0 0003 Typical calculation times in seconds per calculation A calculation returns one property at one state point These times
32. SXT GasPSXT pressure entropy Xy2 Xo2 Xar Xco2 Xuzo unit set returns the temperature of the moist gas Arguments pressure specific entropy MNS Xoz Xan Xcoz XH20 unit set Return Value temperature Examples Description is a value representing the absolute total pressure of the gas in units consistent with the selected unit set is the specific entropy per mass of dry gas in units consistent with the selected unit set and ASHRAE reference point If 16 is added to the unit set entropy is per mass of wet gas If 8 is added to the unit set entropy is referenced to 0 K the gas composition N2 O2 Ar CO2 H20 of the gas Zus Kos Xar and Xco2 are entered as mole fractions of the dry gas with Xuso entered as a humidity ratio All of the five arguments must be entered in order even if any are zero If 32 is added to the unit set all X values are entered as mole fractions of the wet gas If 64 is added to the unit set mass fractions are substituted wherever mole fractions are required 0 or ENG 1 or SI 2 or EngG 3 or SIF 4 or SIK 5 or MET 6 or METF Description is the gas s dry bulb temperature in units consistent with the selected unit set If the resulting temperature is below the dew point the value accounts for the condensed water Examples gt EE RE ER RE urn ee Ee P 14 696 psia S 0 1154 Btu Ib F N2 0 740285 O2 0 198589 Ar 0 008855 CO2 0
33. TABLE 17 SPECIFIC HEAT OF OXYGEN Temperature Pressure Range From deg K 180 260 10 60 410 10 10 710 810 1500 IR a 2 Error Error Error Error Error Error 250 0 043 0 122 0 466 1 381 2 495 8 550 250 huen o 122 0 466 1 381 2 495 1450 10 001 0 001 0 005 0 008 0 017 0 029 1450 0 001 0 001 0 005 0 008 0 017 2000 0 000 0 001 0 003 0 004 0 011 0 016 2000 0 000 0 001 0 003 0 004 0 011 COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 18 SPECIFIC HEAT OF ARGON Temperature Pressure Range From deg K 180 260 10 60 410 510 10 710 810 1500 deg K Avg Max Avg Max Avg Max Error Error Error Error Error Error 250 J0 031 0 093 0 517 1 643 1 574 4 820 Gas for Windows Version 3 2 User s Manual Page 41 Chapter 5 Speed and Accuracy Page 42 COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 19 SPECIFIC HEAT OF CARBON DIOXIDE Range hE e EE E Error Error Error Error Error Error 410 1500 J0 004 0 007 0 065 0 078 0 184 0 286 710 800 Jones 0 007 0 005 0 017 0 021 0 043 10 1450 0 006 0 013 0 009 0 016 0 072 0 206 NBS data not available COMPARISON OF RESULTS WITH ASME 6 DATA TABLE 20 SPECIFIC HEAT OF WATER VAPOR Temperature Pressure Range deg K deg K Avg Max Avg Max Avg Max Error Error Error Error Error Error 610 on onse 0 080 0 045 0 075 0 146 0 302 Gas
34. ach of the gas property functions in either the Form code or in the Global code The DECLARE statement must include the name of the function the dynamic link library where it can be found TGAS32 DLL and the list of arguments which must all be passed by value ByVal A sample DECLARE statement follows Declare Function GasPTXH Lib TGAS32 DLL ByVal P As Double ByVal T As Double ByVal N2 As Double ByVal O2 As Double ByVal Ar As Double ByVal CO2 As Double ByVal H20 As Double ByVal Unitset As Integer As Double A text file TGASVBDEC TXT which lists declarations for all of the Gas functions is copied to a Programming folder in the Gas program folder if the Programming option was selected during installation If you are using the Gas functions in an Excel Visual Basic module to create additional functions you should use a different name to declare the functions or they will conflict with the functions in the Xlgas32 xll add in In this case you must use the ALIAS keyword in the declaration to identify the true name in the DLL For example Declare Function MyGasPTXH Lib TGAS32 DLL ALIAS GasPTXH ByVal P As Double ByVal T As Double ByVal N2 As Double ByVal O2 As Double ByVal AR As Double ByVal CO2 As Double ByVal H20 As Double ByVal Unitset As Integer As Double A text file TGASVBADEC TXT which lists declarations for all of the
35. are copyright notice each time the add in is loaded Gas for Windows Version 3 2 User s Manual Chapter 3 Using DeskTop Gas Calculator Page 8 Each time you start Excel the Gas functions will be loaded automatically If you wish to remove the functions use the Add In Manager and uncheck the check box next to Gas for Excel to remove the add in Gas will not load the next time you start Excel until you add it again using the Add In Manager as described above Once the add in is loaded the gas property functions are available in the same ways as Excel s built in functions That is they can be typed into cell formulas or they can be inserted using Excel s Insert Function feature When using this feature the gas property functions will be alphabetically sorted in a function category called Engineering If you need help use the Excel Help menu and select the Gas Help item This will launch an interactive help window which provides information regarding the functions and their usage Generally you can use any of the functions listed in section 2 2 in any cell formula Be sure to prefix the function name with an character if it is the first or only item in a formula The line below presents an example of a call to a gas property function from Excel GasPTXH al bl cl dl el f1 gl1 SI The argument a1 is for the gas pressure and can be a cell reference or an actual pressure value In a similar manner b1
36. as for Windows Version 3 2 User s Manual Appendix Gas Detailed Function Listing Page 64 GasXMW GasXMWI X vs Xoz Xan Xcoz Xuzo unit set returns the molecular weight of the moist gas Arguments Aus Xoz Xan Xcoz XH20 unit set Return Value molecular weight Description the gas composition N2 O2 Ar CO2 H20 of the gas Zus Kos Xar and Xco2 are entered as mole fractions of the dry gas with Xuso entered as a humidity ratio All of the five arguments must be entered in order even if any are zero If 32 is added to the unit set all X values are entered as mole fractions of the wet gas If 64 is added to the unit set mass fractions are substituted wherever mole fractions are required 0 or ENG 1 or SI 2 or EngG 3 or SIF 4 or SIK 5 or MET 6 or METF Description is a value representing molecular weight of the dry gas If 16 is added to the unit set the molecular weight is per mass of wet gas Examples N2 0 740285 O2 0 198589 Ar 0 008855 CO2 0 000298 H2O 0 051973 GasXMW 0 740285 0 198589 0 008855 0 000298 0 051973 48 28 3957 Ibs per mole of wet gas Gas for Windows Version 3 2 User s Manual Appendix I Gas Detailed Function Listing Page 65 GasPHXT GasPHXT pressure enthalpy XN2 Xo2 Xan Xco2 Xuzo unit set returns the temperature of the moist gas Arguments pressure specific enthalpy MNS Xoz Xan Xcoz XH20 unit set Retu
37. be consistent with your input units You may change any of the data and repeat the calculation as required When you are satisfied with the result you may copy that state point back to the Active Point on DeskTop Gas main window by pressing the Close and Copy to Current Point button Note that the values for moist gas in the second column will be copied back to the active point If no condensation has occurred these values will be the same as in the first column labeled mixture If condensation has occurred then the values in the second column will be at saturated conditions If you do not wish to replace the Active Point on the main window with the heating cooling state point calculated just press the Cancel button 3 10 3 Exchanging Data with Other Programs DeskTop Gas includes two ways to share data with other applications running on your PC such as Excel Both methods use the Windows clipboard In the first data sharing method DeskTop Gas Edit Copy command copies whatever text is highlighted in an IO Box e g a number or part of a number to the Windows clipboard From there that text can be pasted into other applications running on your PC This is typically done using those applications Edit Paste command The second data sharing method also places text on the clipboard but uses an extended format that is especially useful for calculations involving gas properties This method is accessed using the Copy Point co
38. can be described by the equation Sp x s Sy lt See 55 x s s xc s2 s bey Ale s Rp ex Ri ap Xy 7 OB C Ba EE AE te XoRT x RT XyRT v oT 2v oT where s ideal gas molar entropy for gas i s constant to adjust reference state for gas i The molar specific heat at constant pressure of a moist gas mixture Cm can be described by the equation Ay FCOXo FEE CeXc TL CR R Bu p pBh uss Xm yp C Ca C NX Cox Cx Cox Cy X m NN o o AA EHE WW ST ST 2y ST ST B dr m C TZ TE v wi va va 2B 3C Ls U v where c ideal gas molar specific heat at constant pressure for gas i 4 1 GAS PROPERTY DATABASE In order to use the equations presented in the previous section to calculate the thermodynamic properties it is necessary to know the B and C virial coefficients of each of the pure gas components and the mixed virial coefficients for all mixture combinations In addition the ideal gas enthalpies entropies and specific heats are required for each gas component Tables of compressibility data for the pure gases and the ideal gas enthalpies entropies and specific heats are provided in reference 1 B and C virial coefficients for the pure gases were obtained by using a least square fit of the compressibility function to isotherms at 10 degree increments from 180 K to 800 K and at 50 degree increments from 800 K to 2000 K Mixed virial coefficients were calculated from mole
39. cted property to scientific notation select the Scientific Notation command from the Format menu or press the EE toolbar button The Format menu many be used to change the number format to Fixed Decimal or Percent as well Corresponding toolbar buttons are Fix and respectively Of course the percent format only makes sense for the non dimensional properties The formatting commands are only enabled when the focus is on an IO Box 3 7 LABELING AND STORING STATE POINTS DeskTop Gas gives you the option of labeling and storing any number of state points for future reference After computing the state point DeskTop Gas will automatically suggest a unique name for the new state point such as Point 1 or Point 2 but you will probably want to enter something more descriptive Just enter a new name in the Point Label box To store this point press the Store Point button The Store button will not be enabled if the displayed data is not a correctly calculated state point DeskTop Gas requires all stored points to have a unique label If you try to store two points with the same label DeskTop Gas will query whether you wish to replace the stored point which has the same label with the current point If not you should rename the point and try to store it again After storing the point the state point values for the active point will be copied into a storage array and given the name you selected The p
40. cular theory using the Leonard Jones 6 12 potential model The following equations were used to calculate the virial coefficients based on the model B T 22N 3 o3B T U C T N 13T o c r j ij Gas for Windows Version 3 2 User s Manual Chapter 4 Theoretical Basis of Gas Functions Page 25 C T 2a 3 etc T where N 6 02205 E per mole Avogadro s number E kT e or T kT e or T kT e iij ij k 1 3807E JIK Boltzmann constant The equations and constants for calculating P and C are found in Hirshfelder Curtis and Bird 4 Values of potential parameters o and ck for the pure gases were obtained by minimizing the errors in predicting the compressibility factors of the pure gases using the Leonard Jones 6 12 potential Mixed potential parameters were obtained by means of the following semi empirical mixing rules Op 05 0 0 ez GER ENE Ou 50 Oin d 0 oh EIE sel Elk Elk leit Leit where 1 0 892 3a 3 Je l En 24N 00 when gas 1 is non water and gas 2 is water or 1 0 when both gases are non water and au polarizability of the apolar molecules ff Se u e0 u dipole moment of the molecule Some of the mixed potential parameters between No Ar and CO with water were determined by Rabinovich 3 based on experimental data on the equilibrium fractional content of water vapor in the solvent gas Where available t
41. described in Reid Prausnitz and Poling 9 4 3 2 Thermal Conductivity In a similar manner to calculate thermal conductivity we treat the gas as a binary mixture of the non polar gases and water vapor For the non polar gas mixture we use the Wassiljewa equation with the Mason and Saxena modification described by Reid Prausnitz and Poling 9 5 ii where S xA A thermal conductivity of the gas mixture A thermal conductivity of component i Gas for Windows Version 3 2 User s Manual Chapter 4 Theoretical Basis of Gas Functions Xx mole fraction of components i and j A 1 0 Hi 2 a wu hau Y R MM amp value that varies from 0 9 to 1 05 as a function of temperature pa exp 0 04647 exp 0 24127 A 4 wi Aaj T lexp 0 04647 exp 2412T 4 C ove 1 6 SEI T P critical temperature and pressure The equation for thermal conductivity of the moist gases is as follows X Y 1 Z Vis where A thermal conductivity of the mixture me pe e E Du Au P U 12 By 15 2725 M 2 MM y2 Los A 1 2 ES 1 m M g Gas for Windows Version 3 2 User s Manual Page 29 Chapter 4 Theoretical Basis of Gas Functions frend E Us aI dr AS ag MP VA Au u 4 AN g ew ri ow 1 1 Fe 15 4MM MA Ay 12 5 Thermal conductivity of dry gas mixture at the specified temperature Page 30
42. e fraction of water vapor can range from 0 to 1 That is there is no limit to the percentage of water vapor in the gas mixture in that situation Elsewhere the mole fraction of water vapor can range from 0 to a limiting saturated value Xeq which is reached when the condensed phase of water is in thermodynamic equilibrium with the gas solution This equilibrium fraction is equivalent to the solubility of the condensed water in the solvent gas mixture In order to facilitate calculation of Xe it is convenient to group the virial coefficients of the non water gases so that the mixture can be treated as a binary mixture between the non water gases and water vapor The virial coefficients of the gas mixture can be expressed as B E 2x x B EN and C x GEET e KT AE E Me g ggg g w ggw g w gww w www where Gas for Windows Version 3 2 User s Manual Chapter 4 Theoretical Basis of Gas Functions Page 22 x mole fraction of the non water gases in mixture x mole fraction of water vapor in the mixture Bo Ca Vitial coefficients of the non water gases P C Virial coefficients of water vapor Boys Cyan Cam Cross virial coefficients Since the sum of the mole fractions of the mixture must equal 1 the value x is equal to 1 Xw The second virial coefficient of the non water gases can be expressed as 2 2 2 2 Diy t BooXo Bir fp Peake 2 D E Byna BycXyXe j AN xy Bo4XoX4 BocXoXc BacX 4X
43. e checking an actual machine you will need to know the exiting gas temperature or enthalpy Check either the Pressure Enthalpy or Pressure Temperature buttons as required The two variables you have chosen will have their value fields enabled all others will be grayed Enter the appropriate values and click the Compute button Gas for Windows Version 3 2 User s Manual Chapter 3 Using DeskTop Gas Calculator Page 18 The Gas Flow In column displays the state point properties entering the equipment which were copied from the active point The Total Flow Out box has three columns that display the state point properties at the end of the expansion The first column identifies the thermodynamic properties for the moist gas mixture and liquid water if any exiting the equipment The second column displays the thermodynamic properties for the moist gas exiting and the third column shows the properties for the liquid water if any condensation occurs The units displayed are those currently in use on DeskTop Gas main window If you wish to use different units you should select those units on the main window before opening the expansion tool Below the state point properties you will find the shaft power based on the entering gas flow rate that you entered The units for these results will be consistent with your input units You may change any of the data and repeat the calculation as required When you are satisfied wi
44. e kees 500 poorte ooo ko kees aoe oos kae 0012 00 poorte H bes 00027 base acne pose 0 000 0 000 0 000 0 001 0 001 0 002 0 005 0 010 me kee 000 nano oom 001 oon cos 0010 200 kee H ker coo oos Jnooa kee COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 4 COMPRESSIBILITY OF CARBON DIOXIDE Temperature Pressure Range deg K DegK Avg Max Avg Max Avg Max Avg Max Error Error Error Error Error Error Error Error bro ber bes pere poor oors Ju na na NA indicates that CO is not in vapor state in this range Gas for Windows Version 3 2 User s Manual Chapter 5 Speed and Accuracy COMPARISON OF RESULTS WITH ASME 6 DATA TABLE 5 COMPRESSIBILITY OF WATER VAPOR Temperature Range Error Error Error ra si wi SCH Gs ne I eed 510 ba o coa Jaana ka Joona boss bose na Ina Pressure op am 01 atm tam tam doam atm 40am atm COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 6 ENTHALPY OF NITROGEN Temperature Pressure Range From egK 180 260 310 360 410 10 610 710 810 1500 degK Avg Max Avg Max Avg Max Error Error Error Error Error Error Gas for Windows Version 3 2 User s Manual Page 35 Chapter 5 Speed and Accuracy Page 36 COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 7 ENTHALPY OF OXYGEN Range RR RR Error Error Error Error Error Error COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 8 ENTHALPY OF ARGON Temperature Pressure Range
45. ections of this chapter describe the calling syntax and other considerations in using the functions within supported applications 2 2 DESCRIPTION OF GAS FUNCTIONS All of the Gas functions which are accessible to the user are summarized in the table below Function Input s Output Equations of State GasPTXV Pressure Temperature Composition Specific Volume GasPVXT Pressure Volume Composition Dry Bulb Temperature GasTVXP Temperature Volume Composition Pressure Thermodynamic Property Functions GasPTXW Saturated Humidity Ratio GasPXD Dew Point Temperature GasXMW Molecular weight GasPTXH Specific Enthalp GasPTXHS Saturated Enthalpy GasPHXT Dry Bulb Temperature GasPTXS Specific Entropy GasPTXSS Saturated Entrop GasPSXT Dry Bulb Temperature GasPTXL Pressure Temperature Composition Mass fraction of water condensed Gas for Windows Version 3 2 User s Manual Chapter 3 Using DeskTop Gas Calculator Transport Property Functions GasPTXC Pressure Temperature Composition Specific Heat GasPTXM Pressure Temperature Composition Viscosity GasPTXK Pressure Temperature Composition Thermal Conductivity Vapor and Liquid Water Property Function GasVapTP Water Vapor Temperature Saturated Pressure GasVapPT Water Vapor Press Saturated Temperature GasCondPTH Pressure Water Temperature Specific Enthalp GasCondPTS Pressure Water Temperature Specific Entropy
46. eral typical calls to the gas property functions The line below presents an example of a call to a gas property function from 1 2 3 GasPTXH al bl cl dl el f1 gl SI The argument a1 is for the gas pressure and can be a cell reference or an actual pressure value In a similar manner b1 is for temperature and c1 through gi are for the gas composition The last argument selects the units set and any options This syntax actually calls an add in function in the 123GAS 12A add in These add in functions perform error checking and return an appropriate 1 2 3 error value e g ERR when necessary typically when input arguments are out of range or when too many arguments are supplied to the function 1 2 3 will not accept a cell formula that contains a function reference with too few input arguments The 123GAS add in functions themselves call functions in TGAS32 DLL to actually perform the calculations 2 5 USING GAS FROM MATHCAD The Gas add in for Mathcad is a self registering DLL All that is required for Mathcad to access the functions is that the add in file MDCGAS32 DLL be located in the MATHCAD USEREFI directory Whenever an Gas function is used Mathcad will automatically load and register the function The Gas add in for Mathcad allows the use of any of the unit sets Mathcad however allows only pure numbers without units to be passed to and from user defined functions The last argument in each function ca
47. ered as mole fractions of the wet gas If 64 is added to the unit set mass fractions are substituted wherever mole fractions are required 0 or ENG 1 or SI 2 or EngG 3 or SIF 4 or SIK 5 or MET 6 or METF Description is the specific enthalpy per mass of dry gas in units consistent with the selected unit set and ASHRAE reference point If 16 is added to the unit set output is per mass of wet gas Examples Ee ee RE PR OE P 14 696 psia T 100 deg F N2 0 740285 O2 0 198589 Ar 0 008855 CO2 0 000298 H20 0 051973 GasPTXC 14 696 100 0 740285 0 198589 0 008855 0 000298 0 051973 48 0 24757 Btu lbm F of wet gas Gas for Windows Version 3 2 User s Manual Appendix Gas Detailed Function Listing Page 58 GasPTXM GasPTXM pressure temperature Xn2 Xoz Xar Xco2 X20 unit set returns the dynamic viscosity of the moist gas Arguments pressure temperature MNS Xoz Xan Xcoz XH20 unit set Return Value viscosity Examples Description is a value representing the absolute total pressure of the gas in units consistent with the selected unit set is a value representing the dry bulb temperature of the gas in units consistent with the selected unit set the gas composition N2 O2 Ar CO2 H20 of the gas Zus Kos Xar and Xco2 are entered as mole fractions of the dry gas with Xuso entered as a humidity ratio All of the five arguments must be ente
48. es although there does not appear to be any definitive standard of accepted values as there are for steam and water We found the most complete coverage by Vasserman Kazavchinskii and Rabinovich 2 who have surveyed the available literature and presented tables of values over a range of temperatures and pressures We have used their tabular values of viscosity and thermal conductivity as the basis of our database for Nitrogen Oxygen Argon and Carbon Dioxide We have used the equations recommended by ASME 6 to compute the viscosity and thermal conductivity properties for water vapor These are the same equations used in our WinSteam product There is little information available regarding the viscosity and conductivity of moist gases In most practical cases the relatively small quantity of water vapor in gas mixtures has a small effect on the overall transport properties unlike the thermodynamic properties which are greatly affected by moisture Nonetheless we have selected a method to account for the effects of moisture on viscosity based on kinetic theory as presented by Hirshfelder Curtis and Bird 4 4 3 1 Viscosity We treat the gas as a binary mixture between the non polar gases N2 O2 Ar and CO and water vapor For the non polar gases the viscosity of the mixture can be calculated as follows Gas for Windows Version 3 2 User s Manual Chapter 4 Theoretical Basis of Gas Functions Page 27 A Ay Hs Ay x Ay Hy H
49. ew data is entered the IO Box is placed in the input mode and a red X appears to the left of the box After a new state point is computed all IO Boxes are placed in the output mode and the red X s are removed The IO Box accepts either numerical values or arithmetic expressions that can be evaluated to a numeric value A number can be entered in either decimal or scientific notation The expression can be any valid arithmetic expression using the following operators T add subtract multiply divide A exponent parentheses Arithmetic calculations can be nested to any level using parentheses An example of a valid expression is 1004 2 99742 2 5 which evaluates to 1000 506 Expressions are evaluated whenever you tab to or click on another control or press the Enter button Only the resulting value is shown in the box If you enter an incorrect expression your computer will beep and the edit cursor will highlight the offending character You must fix the error before DeskTop Gas will allow you to continue If the expression you are entering is too long to fit in the box the box will temporarily increase in length so that you may view more of the expression When you are finished editing the box returns to its original length To recall the last expression used in an input box use the Recall Expression command on the Edit menu You ll then have the opportunity to edit the expression and let the IO
50. f the moist gas Arguments temperature specific volume Xna Xoz Xan Xcoz XH20 unit set Return Value pressure Description is a value representing the dry bulb temperature of the gas in units consistent with the selected unit set is the specific volume per mass of dry gas in units consistent with the selected unit set If 16 is added to the unit set specific volume is per mass of wet gas the gas composition N2 O2 Ar CO2 H20 of the gas Xn2 Kos Xar and Xco2 are entered as mole fractions of the dry gas with Xuso entered as a humidity ratio All of the five arguments must be entered in order even if any are zero If 32 is added to the unit set all X values are entered as mole fractions of the wet gas If 64 is added to the unit set mass fractions are substituted wherever mole fractions are required 0 or ENG 1 or SI 2 or EngG 3 or SIF 4 or SIK 5 or MET 6 or METF Description is a value representing the absolute total pressure of the gas in units consistent with the selected unit set Examples T 100 deg F V 14 387 ft lbm N2 0 740285 O2 0 198589 Ar 0 008855 C02 0 000298 H20 0 051973 GasTVXP 100 14 387 0 740285 0 198589 0 008855 0 000298 0 051973 48 14 696 psia Gas for Windows Version 3 2 User s Manual Appendix Gas Detailed Function Listing Page 53 GasPTXH GasPTXH pressure temperature XN2 Xo2 Xan Xco2 Xnz2o unit set ret
51. fully all property values are recalculated and the red X s are cleared Be sure to enter the values in units consistent with the unit displayed to the right of the value box If you wish to change units select the desired units before entering the value If you change units after the value is entered the value entered will be converted to the new units Next click the Compute button to find all the unknown properties If the Compute button is grayed you have not checked enough properties to define the state point Fields without check boxes are output only These include specific heat viscosity and thermal conductivity and dew point After recalculation all fields contain property values for the gas mixture at a particular state point 3 3 ENTERING DATA Numeric data is entered in a specially designed edit box called an IO Box which behaves like a standard Windows edit box but includes some additional features To enter new data double click the IO Box and all the data will be highlighted As you enter new data the old data will be replaced To edit data hold the left mouse button down and drag the mouse over Gas for Windows Version 3 2 User s Manual Chapter 3 Using DeskTop Gas Calculator Page 14 the characters that you wish to replace thereby highlighting them Release the mouse button and type new characters to replace the highlighted ones The IO Box has two modes of operation input and output When n
52. g Range EE 4 2 2 2 Basic Unit E 5 2 2 37 1 EECHER 5 224 Wetor Dry EE 6 2 2 5 Reference Conditions esene nene eneee ee ee e e ee Ee Ee EE ORE 6 2 3 BREER N N BEER N ei EE 7 2 4 Using Gas TOM lao EE 8 2 5 Using Gas from Mathcad EE 9 2 6 Using Gas from visual BASIC 10 2 7 Using Gas from C C Windows Programming Languages sesse ekke 10 2 8 Version and REEL EE 11 USING DESKTOP GAS CALCULATOR sse 12 3 1 NVC EEN 12 3 2 Basi EE ar re eeh Ee ee Ee 12 3 3 Entering ST 13 3 4 Unit Seleeiionzz a 222er aber 14 3 5 Calculating State POS eege gege Ee DER Re BE DR Ee DR DR ee BR Ee DE DS ee BR ER Re ER Re ER 15 3 6 Formatting Property Values 15 3 7 Labeling and Storing State Points 16 3 8 POUT UNG ton i als tod RD DA AA AA AR DA 16 3 9 Saving And Opening Data Files sees SERE ESE ESE ES SEGE SEER SEG ER ee EER send ee ed 17 TABLE OF CONTENTS 3 10 Advanced Features EE GE EER ces eos GEGEE asec ate cae ee GE EED Ee 17 3 10 1 Expansion Compression Kee ME 17 3 10 2 Heating Cooling R Re EE 18 3 10 3 Exchanging Data with Other Programme 19 3 11 Getting IG e EE 19 3 12 SEENEN EE 20 3 13 Exiting DeskTop e 20 4 THEORETICAL BASIS OF GAS FUNCTIONS sse eee eee 21 4 1 Gas Property Database ass stelle 24 4 2 Computational Model EE 26 4 3 Transport Properli S sae ee EE BR OE EG EG EE OE OE Ee ee Ge ee 26 48 VISCOS Ee os ho fon N fon So Soon AE fn Jo fot Sod foo Sod fo ho fon So foo he Did Joa 26 4 3 2 Thermal Conductivity
53. greement with this data As with the thermodynamic properties the accuracy of the mixing equations for the transport properties are illustrated by comparison with dry air These comparisons are shown in Table 43 The mixing equations for the transport properties are not as precise as those for the thermodynamic properties however in most cases the errors are less than 1 Gas for Windows Version 3 2 User s Manual Chapter 5 Speed and Accuracy Page 33 COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 1 COMPRESSIBILITY OF NITROGEN Pressure Range Error Error Error Error Error Error Error Error 510 Fa _ 000 o 000 ooo0 poor oor oooa poor Dans COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 2 COMPRESSIBILITY OF OXYGEN Tempe Pressure Ran rature ge Error Error Error Error Error Error Error Error 2 3 3 4 5 7 8 1 Gas for Windows Version 3 2 User s Manual Chapter 5 Speed and Accuracy Page 34 COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 3 COMPRESSIBILITY OF ARGON Temperature Pressure Range deg K DegK Avg Max Avg Max Avg Max Avg Max Error Error Error Error Error Error Error Error 180 0 000 0 001 0 001 0 002 0 004 0 007 0 071 0 213 180 _ 1250 _10 000 0 001 1 001 o 002 bom bas 0 071 0 213 er e Jono ooo core bor oos aon oase Ioaox Bro e kee o oo aco Joo oos ons pose kee 250 300 350 400 500 700 800 1450 200 poorte o oo ko ker core kee ka
54. he following e Click the upper left corner of its program window and select close from the menu e Select Exit from the File menu e Press Alt F4 keys e Click the X button in the upper right corner of the program window Gas for Windows Version 3 2 User s Manual Chapter 4 Theoretical Basis of Gas Functions Page 21 4 THEORETICAL BASIS OF GAS FUNCTIONS It is commonly accepted that virial equations of state work well for gases In Gas the P V T behavior of a gas mixture is described by a third order virial equation of state B C AR T N RT v v where p Total pressure T Absolute Thermodynamic Temperature v Total volume of gas R Universal Gas Constant B_ second order virial coefficient of the mixture C third order virial coefficient of the mixture For the ranges of pressure and temperature used in these functions coefficients higher than third order can be ignored It is important to note that Bm and Cm are functions only of temperature Over the range of temperatures and pressures covered by these functions all of the gases except water exist only in the gaseous state Actually CO can exist in a liquid state at the high end of the pressure range and the low end of the temperature range but this state is not considered because it would only occur in a mixture that is almost pure CO2 At temperatures where the saturation pressure of pure water is greater than the total gas pressure the mol
55. hese mixed potential parameters were used instead of the ones derived from the mixing rules Gas for Windows Version 3 2 User s Manual Chapter 4 Theoretical Basis of Gas Functions Page 26 Based on the methods described a database was developed containing all of the pure gas and mixed virial coefficients for the five gases at 10 degree increments from 180 K to 800 K and at 50 degree increments between 800 K and 2000 K A similar database was developed for the ideal gas enthalpies entropies and specific heats 4 2 COMPUTATIONAL MODEL With most of the functions the mixture s pressure and temperature are known Since the virial coefficients are functions only of temperature the database is used to calculate mixed coefficients Byg Dou Baw Logg Cagw Lou and Cwww based on the formulas identified above at four temperatures surrounding the desired temperature Four point non linear interpolation is used to calculate the mixed coefficients and their derivatives at the desired temperature Since most of the properties require knowledge of the specific volume of the mixture the virial equation of state is used iteratively to calculate the specific volume In cases where the temperature of the mixture is not known iterative procedures are used to determine the temperature as well 4 3 TRANSPORT PROPERTIES Values for viscosity and thermal conductivity of individual gases at atmospheric pressure can be found in many referenc
56. ies listed in a row A label for each row includes the property name and the current units selected The printing utility will attempt to fit as many points on a page as possible based on the paper size and orientation that you specify using the Print Gas for Windows Version 3 2 User s Manual Chapter 3 Using DeskTop Gas Calculator Page 17 Setup command You can preview the output by selecting the Print Preview command from the File menu 3 9 SAVING AND OPENING DATA FILES When you start DeskTop Gas or open a new file it will be untitled You may save a collection of stored state points along with your selections of units and formats to a DeskTop Gas file Select Save from the File menu or click the disk icon on the toolbar which will open the Save As dialog box You should enter a name for the file the file extension gas will be added automatically You may choose a folder in which to save the file or accept the default folder If you have saved the file at least one time during the session you can save the work under a different filename by choosing the Save As command from the File menu To open a saved file select Open from the File menu or click the open file icon on the toolbar This will open a dialog box that lists all of your DeskTop Gas data files in the current folder You may select a different folder to view other files Select the file you want to open and press the O
57. ll is the unit set designator and can have a value from 0 to 127 depending upon the selection of base unit set and the unit set options The other arguments to the function must be numbers without units whose values are consistent with the selected unit set The Gas package contains a sample Mathcad file named EXAMPLE MCD which makes typical calls to the gas property functions and illustrates the use of the unit set designator Although on line help for Gas is not directly available from within Mathcad the Choose function feature does recognize the Gas functions and assists user with the functions Use Gas for Windows Version 3 2 User s Manual Chapter 3 Using DeskTop Gas Calculator Page 10 the Math Choose Function menu selections to open the Choose Function window Scroll down the Function name is box to find all of the gas functions listed in alphabetical order The Returns box will describe the input arguments and the return value for the function that is selected Pressing the Insert push button will copy the function to your worksheet with placeholders for each function argument 2 6 USING GAS FROM VISUAL BASIC The gas property functions can be used directly in your Visual Basic programs just like the built in functions Before the functions can be used however they must be declared as functions and Visual BASIC must be told where to find them This can all be accomplished by including a DECLARE statement for e
58. missed for two reasons First dissociation effects were not included below 1500 K in reference 1 Second the error is much greater than what can be attributed to dissociation above 1500 K Further examination of the data tables suggests that the tables in reference 1 are in error One would expect the thermodynamic properties to approach the ideal gas properties as the pressure is reduced to zero While this is the case for temperatures up to 800 K it is not the case above 800 K Curiously at 800 K the tables in reference 1 change from a temperature increment of 10 K to 50 K at the point where the error begins Perhaps this change of temperature increment was not handled properly Comparison of data from Vasserman et al 2 in the temperature range from 850 K to 1300 K supports the conclusion that the tables from NBS 1 are in error Unfortunately the tables from Vasserman et al 2 do not contain data for temperatures above 1300 K Thermodynamic properties for moist air are presented by ASHRAE 10 at atmospheric pressure for temperatures up to 200 deg C The ASHRAE data is based on work done by Hyland and Wexler 8 who provide tables of calculated data at pressures up to 50 bar Comparisons with this data are shown on Tables 29 through 40 Data for Viscosity and Thermal Conductivity is taken from Vasserman et al 2 for the pure gases except for water vapor which is taken from ASME 6 Tables 41 and 42 show excellent a
59. mmand on the Ed menu Regardless of whether any text is selected this command copies a table of text values to the clipboard using either the Active Point or all of the stored points The table includes one column for each point You can optionally direct DeskTop Gas to also include property and unit labels in which case they appear as the first column in the table The table includes one row for each property in the same order as they are displayed on DeskTop Gas main window All values are copied to the clipboard using the same format displayed on the screen So if you need more accuracy in your Excel calculations set the DeskTop Gas display accuracy accordingly before issuing the Copy Point command 3 11 GETTING HELP The Help menu offers extensive on line help for DeskTop Gas The About item in the Help menu presents the version and serial numbers of your copy of Gas If the program is running in its Demo mode the number of days remaining on the Demo are displayed instead of a serial number Gas for Windows Version 3 2 User s Manual Chapter 3 Using DeskTop Gas Calculator Page 20 3 12 ERROR MESSAGES When input values are out of range or any other errors occur a message box is displayed describing the error The calculated fields will not be updated until the error condition is resolved 3 13 EXITING DESKTOP GAS You may exit DeskTop Gas by using any of the standard methods for closing Windows applications These include t
60. mples P 14 696 psia T 50 deg F N2 0 740285 O2 0 198589 Ar 0 008855 CO2 0 000298 H20 0 051973 GasPTXL 14 696 50 0 740285 0 198589 0 008855 0 000298 0 051973 32 0 02556 Ibm of water Ibm of wet gas Gas for Windows Version 3 2 User s Manual Appendix Gas Detailed Function Listing Page 68 GasVapPT GasVapPT pressure unit set returns the saturation temperature of the water vapor Arguments Description pressure is a value representing the absolute total pressure of gas in units consistent with the selected unit set unit set 0 or ENG 1 or SI 2 or EngG 3 or SIF 4 or SIK 5 or MET 6 or METF Return Value Description temperature is a value representing the saturation temperature of water vapor in units consistent with the selected unit set Examples EA P 14 696 psia GasVapPT 14 696 0 211 95 deg F Gas for Windows Version 3 2 User s Manual Appendix I Gas Detailed Function Listing Page 69 GasVapTP GasVapPT temperature unit set returns the saturation temperature of the water vapor Arguments Description temperature is a value representing the temperature of the gas in units consistent with the selected unit set unit set 0 or ENG 1 or SI 2 or EngG 3 or SIF 4 or SIK 5 or MET 6 or METF Return Value Description pressure is a value representing the saturation pressure of water vapor in units consis
61. n Kaes 1 1 fo oo2 ko rio be kom Ra Kr baa en ke bo oooox ba bal T 1500 2000 ko i000 nano ooon NBS data not available COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 14 ENTROPY OF CARBON DIOXIDE Range From fo tam oam aan deg K deg K Avg Max Avg Max Avg Max al Se zo na D Io NA NA Im 260 soo boo oos poes Daran na mn 10 ba kor 1 pos pose os so Je bes kae kae koer kee loose 10 500 pos 0 04 oos loose In020 kees ro ber ka 1 bes fo o10 oe 10 rn oos oor loose pos kom oo 710 be bass 1 loor oor a10 ba ko Kos 002 boo 003 ber mm be EE NBS data not available Gas for Windows Version 3 2 User s Manual Chapter 5 Speed and Accuracy COMPARISON OF RESULTS WITH ASME 6 DATA TABLE 15 ENTROPY OF WATER VAPOR Temperature Pressure Range deg K Avg Max Avg Max Avg Max Error Error Error Error Error Error NA NA From deg K 180 290 80 460 40 10 710 50 1500 NA NA 700 0 022 0 022 0 025 0 025 0 026 0 028 Too pozze kee pose 00207 COMPARISON OF RESULTS WITH NBS 1 DATA TABLE 16 SPECIFIC HEAT OF NITROGEN Temperature Pressure Range From deg K 180 260 10 60 410 10 10 710 810 1500 deg K Avg Max Avg Max Avg Max Error Error Error Error Error Error 250 0 062 0 182 0 758 2 899 2 923 9 543 Gas for Windows Version 3 2 User s Manual Page 40 Chapter 5 Speed and Accuracy COMPARISON OF RESULTS WITH NBS 1 DATA
62. n next to each gas component It indicates the basis of the gas composition Initially the label should indicate Vol frac Dry which means that the gas composition is entered as a volume or mole fraction on a dry basis Note that the value for water vapor is zero and the box is read only This ensures that you can only enter water vapor as a humidity ratio If you want to enter the composition on a wet basis press the button labeled Change to Wet Composition Now you will find that the humidity ratio is read only and water vapor box is enabled If you want to enter the composition as mass fractions instead of mole fractions press the button labeled Change to Mass Fraction The other button in the gas composition section resets the gas composition to all zeros If you want the mass dependent properties to be expressed on a wet basis instead of a dry basis press the button labeled Change to per Wet Mass Next select the input properties by selecting the corresponding check boxes as described above Enter values for those properties in the boxes to the right of the property names The next section describes various methods for entering data When you enter a value for any of the key properties a red X appears next to the property value to indicate that a new value has been entered This is a warning that the value being displayed is not consistent with the current state point After a compute command is completed success
63. oint will be displayed in the stored points column in same units as the active point After a state point is stored its name is added to the point name combo box in the upper right hand corner of the main window You can view a stored point by pressing the arrow on the point name combo box and selecting a point from the drop down list If you wish to use a stored point with any of the special tools or as the basis for calculating a new point you must recall the stored point to the active point Begin by selecting the point from the point name combo box s dropdown list Next press the Recall Point button to copy the stored point to the active point You may now use the active point for new calculations If you change any input data and press Compute the active point will be changed but the stored point from which you copied the values will remain intact You can delete a stored point by first selecting it from the Point Name combo box and then select Delete Point from the Ed menu This collection of state points can be saved as a DeskTop Gas file In addition you can copy state points to the clipboard where they can be transferred to another application such as a spreadsheet program or word processor 3 8 PRINTING You can print a table consisting of all of the stored points by selecting the Print command from either the file menu or the toolbar The tables will include a column for each of the stored points with each of its propert
64. omposition and any two of the other five properties In most practical applications pressure is usually one of the known variables Most of the calculations require that the pressure be known In the rare case when pressure is not known it can be calculated from the equation of state if the dry bulb temperature and specific volume are known Gas for Windows Version 3 2 User s Manual Chapter 3 Using DeskTop Gas Calculator Page 13 Each of the key properties has a check box associated with it When checked it signifies that this property is to be used in calculating the state point In general two thermodynamic properties and the gas composition must be selected before DeskTop Gas will allow a computation If pressure and temperature are selected DeskTop Gas can compute the gas properties in the state that is saturated with water vapor In these cases you will notice that the Compute Saturated button is enabled Once you select one property DeskTop Gas will disable all the other check boxes whose properties are not allowed in combination with the first selected property You may change your selections by un checking one or all of the check boxes and selecting a new combination To compute a gas property state point begin by entering the gas composition in the lower half of the calculator If you wish to use the composition for standard dry air press the button labeled Set to Standard Dry Air Note the label in the units colum
65. or word processor Major features of this program include validity over Gas s full range of pressures and temperatures flexible interactive design large choice of units for each property tools for heating cooling expansion and compression processes instant response time extensive help screens O O O O O 0 If installed properly DeskTop Gas is started by simply double clicking on its name icon in the Gas subgroup of the TechwareEng Group appearing on the Windows Start Menu 3 2 BASIC OPERATION The DeskTop Gas display is arranged in a tabular format that remains constant although the program window can be re sized You may sometimes find it convenient to make the program window smaller Each of the rows in the top section is dedicated to one of the gas properties pressure temperature specific volume enthalpy entropy specific heat dynamic viscosity thermal conductivity and dew point temperature Each of the rows in the Gas Composition section shows the fraction of one of the individual gasses as well as the humidity ratio and molecular weight of the mixture There is a column that displays the property values for the active point and a column that displays data for one of the stored points The key properties that can be used to define the gas state point are pressure temperature specific volume enthalpy entropy and the gas composition Theoretically a state point can be uniquely identified by specifying the gas c
66. pen button to load the file To start a new file select the New button from the Toolbar If you have stored any points and have not saved the file you will be prompted to do so 3 10 ADVANCED FEATURES DeskTop Gas includes special tools that facilitate the calculation of some common gas processes These tools include an Expansion Compression tool and a Heating Cooling tool 3 10 1 Expansion Compression Tool The Expansion Compression tool is used to evaluate performance of a gas turbine or an air compressor If you are predicting the performance and know the efficiency of the turbine or compressor the tool can be used to calculate the state point conditions at the expansion or compression end point If you are analyzing the performance of a turbine or compressor and know the conditions at the end point the tool can be used to calculate the efficiency The tool also computes the energy converted to shaft work generated by the turbine or used by the compressor To use the tool first select the active state point representing the start of the expansion or compression path Next select Expand Compress from the Tools menu or click the turbine icon on the toolbar which will open the Expansion Compression tool dialog box In the tool dialog box select the conditions you will use to compute the end point from the combo box near the top of the screen Select Pressure amp Efficiency if you know the pressure and efficiency If you ar
67. pplications e g Excel 1 2 3 etc 3 5 CALCULATING STATE POINTS When you have finished entering values for the selected input variables click the on screen button labeled Compute to calculate all of the state point properties If the Compute button is grayed you have not checked enough properties to define the state point You may also compute the state point by pressing the Enter key on your keyboard Note that the Enter key serves two purposes in DeskTop Gas Pressing the Enter key just after entering data in an IO Box tells DeskTop Gas to evaluate the expression in the IO Box Pressing the Enter key a second time tells DeskTop Gas to compute the state point If you move the focus to any other control after entering data in an IO Box the expression is evaluated automatically and you only have to press the Enter key only once to compute the state point The Enter key will not compute a state point if the Compute button is grayed 3 6 FORMATTING PROPERTY VALUES DeskTop Gas normally displays all property values in fixed decimal notation You may increase or decrease the number of decimal places in a selected property IO Box by selecting Add Decimal Places or Decrease Decimal Places from the Format menu or by clicking 0 1 00 either of the FIE1 toolbar buttons respectively Gas for Windows Version 3 2 User s Manual Chapter 3 Using DeskTop Gas Calculator Page 16 If you wish to change the sele
68. red as mole fractions of the dry gas with Xuso entered as a humidity ratio All of the five arguments must be entered in order even if any are zero If 32 is added to the unit set all X values are entered as mole fractions of the wet gas If 64 is added to the unit set mass fractions are substituted wherever mole fractions are required 0 or ENG 1 or SI 2 or EngG 3 or SIF 4 or SIK 5 or MET 6 or METF Description is the specific volume per mass of dry gas in units consistent with the selected unit set If 16 is added to the unit set output is per mass of wet gas Examples P 14 696 psia T 100 deg F N2 0 740285 O2 0 198589 Ar 0 008855 CO2 0 000298 H20 0 051973 GasPTXW 14 696 100 0 740285 0 198589 0 008855 0 000298 0 051973 32 0 04324 Ibm water vapor lbm of dry gas Gas for Windows Version 3 2 User s Manual Appendix Gas Detailed Function Listing Page 61 GasPXD GasPXD pressure Xn2 Xoz Xan Xco2 Xn2o unit set returns the dew point temperature of the moist gas Arguments pressure Xna Xoz Xan Xcoz XH20 unit set Return Value dew point temperature Description is a value representing the absolute total pressure of the gas in units consistent with the selected unit set the gas composition N2 O2 Ar CO2 H20 of the gas Xj2 Xo2 Xar and Xco2 are entered as mole fractions of the dry gas with Xuso entered as a humidity ratio All of the fi
69. red in order even if any are zero If 32 is added to the unit set all X values are entered as mole fractions of the wet gas If 64 is added to the unit set mass fractions are substituted wherever mole fractions are required 0 or ENG 1 or SI 2 or EngG 3 or SIF 4 or SIK 5 or MET 6 or METF Description is the dynamic viscosity based on the flow of dry gas in units consistent with the selected unit set and ASHRAE reference point If 16 is added to the unit set output is based on the mass of wet gas SU P 14 696 psia T 100 deg F N2 0 740285 O2 0 198589 Ar 0 008855 CO2 0 000298 H20 0 051973 GasPTXM 14 696 100 0 740285 0 198589 0 008855 0 000298 0 051973 48 0 0457 lbm hr ft of wet gas Gas for Windows Version 3 2 User s Manual Appendix Gas Detailed Function Listing Page 59 GasPTXK GasPTXK pressure temperature Xn2 Xo2 Xar Xco2 X20 unit set returns the thermal conductivity of the moist gas Arguments pressure temperature MNS Xoz Xan Xcoz XH20 unit set Return Value conductivity Examples Description is a value representing the absolute total pressure of the gas in units consistent with the selected unit set is a value representing the dry bulb temperature of the gas in units consistent with the selected unit set the gas composition N2 O2 Ar CO2 H20 of the gas Zus Kos Xar and Xco2 are entered as mole fractions of the d
70. rmodynamic Properties of Ordinary Water Substance for General and Scientific Use International Association for the Properties of Water and Steam Paris France September 1995 R W Hyland A Wexler 1983 Formulations for the Thermodynamic Properties of Dry Air from 173 15 K to 473 15 K and of Saturated Moist Air from 173 25 K to 372 15 K at Pressures to 5 MPa ASHRAE Transactions 89 2A 520 35 Robert C Reid John M Prausnitz Bruce E Poling The Properties of Gases and Liquids Fourth Edition McGraw Hill Inc American Society of Heating Refrigeration and Air Conditioning Engineers ASHRAE Fundamentals 1993 Gas for Windows Version 3 2 User s Manual Appendix Gas Detailed Function Listing Page 49 APPENDIX DETAILED FUNCTION LISTING This section contains detailed descriptions of each of the Gas functions which can be called from the GASPRP32 DLL or GASPROPS DLL as listed below e GasPTXV e GasPVXT e GasTVXP e GasPTXH e GasPTXS e GasPTXHS e GasPTXSS e GasPTXC e GasPTXM e GasPTXK e GasPTXW e GasPXD e GasXW e GasWX e GasXMW e GasPHXT e GasPSXT e GasPTXL e GasVapPT e GasVapTP e GasCondPTH e GasCondPTS e GasVer Gas for Windows Version 3 2 User s Manual Appendix Gas Detailed Function Listing Page 50 GasPTXV GasPTXV pressure temperature Xn2 Xo2 Xar Xco2 X20 unit set returns the specific volume of the moist gas Arguments pressure temperature
71. rn Value temperature Examples Description is a value representing the absolute total pressure of the gas in units consistent with the selected unit set is the specific enthalpy per mass of dry gas in units consistent with the selected unit set and ASHRAE reference point If 16 is added to the unit set enthalpy is per mass of wet gas If 8 is added to the unit set enthalpy is referenced to 0 K the gas composition N2 O2 Ar CO2 H20 of the gas Zus Kos Xar and Xco2 are entered as mole fractions of the dry gas with X20 entered as a humidity ratio All of the five arguments must be entered in order even if any are zero If 32 is added to the unit set all X values are entered as mole fractions of the wet gas If 64 is added to the unit set mass fractions are substituted wherever mole fractions are required 0 or ENG 1 or SI 2 or EngG 3 or SIF 4 or SIK 5 or MET 6 or METF Description is the gas s dry bulb temperature in units consistent with the selected unit set If the resulting temperature is below the dew point the value accounts for the condensed water Examples EE ee P 14 696 psia H 59 657 Btu lb N2 0 740285 O2 0 198589 Ar 0 008855 CO2 0 000298 H20 0 051973 GasPHXT 14 696 59 657 0 740285 0 198589 0 008855 0 000298 0 051973 48 100 deg F Gas for Windows Version 3 2 User s Manual Appendix Gas Detailed Function Listing Page 66 GasP
72. ry gas with Xuso entered as a humidity ratio All of the five arguments must be entered in order even if any are zero If 32 is added to the unit set all X values are entered as mole fractions of the wet gas If 64 is added to the unit set mass fractions are substituted wherever mole fractions are required 0 or ENG 1 or SI 2 or EngG 3 or SIF 4 or SIK 5 or MET 6 or METF Description is the thermal conductivity of the gas mixture in units consistent with the selected unit set Examples oo ee me tn m seen er P 14 696 psia T 100 deg F N2 0 740285 O2 0 198589 Ar 0 008855 CO2 0 000298 H20 0 051973 GasPTXK 14 696 100 0 740285 0 198589 0 008855 0 000298 0 051973 32 0 01544 Btu hr fU F Gas for Windows Version 3 2 User s Manual Appendix Gas Detailed Function Listing Page 60 GasPTXW GasPTXW pressure temperature Xn2 Xo2 Xar Xco2 X20 unit set returns the saturated humidity ratio of the moist gas Arguments pressure temperature Xna Xoz Xan Xcoz XH20 unit set Return Value humidity ratio of gas saturated with water vapor Description is a value representing the absolute total pressure of the gas in units consistent with the selected unit set is a value representing the dry bulb temperature of the gas in units consistent with the selected unit set the gas composition N2 O2 Ar CO2 H20 of the gas Zus Kos Xar and Xco2 are ente
73. splayed in SI units You can change all of the units to either standard English or SI units by issuing the English Units or SI Units command from the Format menu or pressing the Eng or SI toolbar button When you change to English units in this manner the reference temperature for the dry gas is changed to 0 F Similarly when changing to SI units the reference temperature is changed to 0 C If you change the units one at a time the reference temperature will not change even if you change all of the units from English to SI units You can force a change in the reference temperature by pressing the Ref button on the toolbar or by selecting Options from the Tools menu and then choosing the Reference Point tab From either of the dialog boxes you will be able to select the desired reference temperature You may choose any combination of available units for your personal default unit set Simply select the units you desire for each property and issue the Make Current Settings Default command from the Format menu The next time you start DeskTop Gas your default unit set will be used If you change units and then save a file those selected units will be restored whenever the file is opened If you wish to change the units back to your default unit set issue the command Restore Default Settings from the Format menu Unit system changes in DeskTop Gas do not affect use of Gas from any other a
74. st gas Arguments pressure specific volume Xna Xoz Xan Xcoz XH20 unit set Return Value temperature Description is a value representing the absolute total pressure of the gas in units consistent with the selected unit set is the specific volume per mass of dry gas in units consistent with the selected unit set If 16 is added to the unit set specific volume is per mass of wet gas the gas composition N2 O2 Ar CO2 H20 of the gas Xn2 Kos Xar and Xco2 are entered as mole fractions of the dry gas with Xuso entered as a humidity ratio All of the five arguments must be entered in order even if any are zero If 32 is added to the unit set all X values are entered as mole fractions of the wet gas If 64 is added to the unit set mass fractions are substituted wherever mole fractions are required 0 or ENG 1 or SI 2 or EngG 3 or SIF 4 or SIK 5 or MET 6 or METF Description is a value representing the dry bulb temperature of the gas in units consistent with the selected unit set Examples P 14 696 psia V 14 387 Dm N2 0 740285 O2 0 198589 Ar 0 008855 CO2 0 000298 H20 0 051973 GasPVXT 14 696 14 387 0 740285 0 198589 0 008855 0 000298 0 051973 48 100 deg F Gas for Windows Version 3 2 User s Manual Appendix Gas Detailed Function Listing Page 52 GasTVXP GasTVXP temperature volume Xn2 Xo2 Xan Xco2 Xn2o unit set returns the pressure o
75. state at the triple point or some other specified temperature We believe that setting the zero point for enthalpy and entropy to water in the liquid state rather than in the vapor state has two major advantages First the values are numerically equivalent to standard international steam tables and Techware s WinSteam product This facilitates the handling of processes that include both moist gas and liquid water streams without worrying about reference temperatures Second It greatly simplifies analysis of processes in which water is either condensed from or evaporated to the gas stream All of Gas reference conditions use the International Temperature Scale of 1990 ITS 90 as the basis of temperature 2 3 USING GAS FROM EXCEL You must load the XLGAS32 XLL add in to access the gas property functions from Excel Loading this add in brings the functions into memory and links them to Excel You can load the Gas property functions into Excel using Excel s Add in Manager as described below The Gas add in works with all 32 bit versions of Excel including Office 2000 and XP Use the Tools Add Ins menu selection to start Excel s Add In Manager If installed using the default values the file XLGAS32 XLL should be in either the EXCEL LIBRARY or the OFFICE LIBRARY directory and the Add In Manager will show that Gas for Excel is available Click the check box next to Gas for Excel and press OK A message will display the Techw
76. tNumber O72 Molecular Weight Mass per Mass per Mass per Mass per Massper Massper Mass per mole mole mole mole mole mole mole 2 2 3 Gas Composition The term Comp used in the table at the beginning of section 2 2 refers to the gas composition which is entered as five sequential variables in the function parameter list Five Gas for Windows Version 3 2 User s Manual Chapter 3 Using DeskTop Gas Calculator values must be entered even if some of the values are zero and they must be in the order No O2 Ar CO and H20 By default the value for each gas constituent is entered as a mole fraction or percent volume on a dry basis The H20 component is entered as a humidity ratio mass of moisture per mass of dry gas This is the same convention used by ASHRAE to handle air properties This convention is useful in some applications where the process includes heating cooling humidification or drying The gas composition does not change except perhaps for the quantity of moisture making it more convenient to express the gas composition on a dry basis with a humidity ratio By default all of the mass dependent properties volume enthalpy entropy specific heat and viscosity are expressed on a basis of dry gas This is also the basis of Techware s Air functions allowing the two add ins to be used together In other cases where the process may involve combustion the composition of all the gas components will change and
77. tent with the selected unit set Examples T 211 95 deg F GasVapTP 211 95 0 14 696 psia Gas for Windows Version 3 2 User s Manual Appendix Gas Detailed Function Listing Page 70 GasCondPTH GasCondPTH pressure temperature unit set returns the specific enthalpy of compressed water Arguments Description pressure is a value representing the absolute total pressure in units consistent with the selected unit set temperature is a value representing the temperature of the water in units consistent with the selected unit set unit set 0 or ENG 1 or SI 2 or EngG 3 or SIF 4 or SIK 5 or MET 6 or METF Return Value Description specific enthalpy is the specific enthalpy per mass of water in units consistent with the selected unit set and referenced to saturated liquid water at the triple point Examples P 14 696 psia T 100 deg F GasCondPTH 14 696 100 0 68 052 Btu lbm Gas for Windows Version 3 2 User s Manual Appendix I Gas Detailed Function Listing Page 71 GasCondPTS GasCondPTS pressure temperature unit set returns the specific entropy of compressed water Arguments Description pressure is a value representing the absolute total pressure in units consistent with the selected unit set temperature is a value representing the temperature of the water in units consistent with the selected unit set unit set 0 or ENG 1 or SI 2 or EngG
78. th the result you may copy that state point back to the active point on DeskTop Gas main window by pressing the Close and Copy to Current Point button Note that the values of moist gas in the second column will be copied back to the active point If no condensation has occurred these values will be the same as in the first column labeled mixture If condensation has occurred then the values in the second column will be at saturated conditions If you do not wish to replace the current point on the main window with the expansion end point calculated just press the Cancel button 3 10 2 Heating Cooling Tool The Heating Cooling tool is used to analyze a gas stream in which heat is either added or removed If you know the quantity of heat that is being added to or removed from the air stream you can use the tool to calculate the resulting state point temperature and other conditions If you know the temperature or enthalpy of the gas leaving the heating or cooling device you can use the tool to calculate the quantity of heat exchanged To use the tool first make sure that the active state point represents the conditions of the air entering the heating or cooling device Next select Heat Cool from the Tools menu or click the flame icon on the toolbar which will open the Heating Cooling tool dialog box In the tool dialog box select the conditions you will use to compute the end point from the combo box near the top of the screen Select
79. ts however ASHRAE uses a reference condition of 0 F at one atmosphere of pressure for dry air properties while maintaining the convention of using the triple point as a reference temperature for water properties For dry gas the Gas functions use a reference temperature of 0 F if an English unit set is selected or 0 C if an SI or Metric unit set is selected DeskTop Gas provides more flexibility as described in section 3 Gas always references water vapor to the triple point of liquid water If you try to convert enthalpy or entropy values produced by the functions from English to SI units simply using standard conversion factors you will find a difference equal to the difference in dry gas enthalpy or entropy between 0 F and 32 018 F You can avoid this problem by converting the input parameters e g pressure and temperature to either English or SI units before calling the desired Gas function As an alternative you can set the reference temperature for the dry gas portion to absolute zero 0 K by adding an A to the unit set name or adding 8 to the unit set number In this case the 0 K reference temperature will be used for any of the English or SI unit sets Please note that in all cases the enthalpy and entropy of the water portion are set to zero for liquid water at the triple point Some publications which are based on perfect gas assumptions assign the zero point for enthalpy and entropy to water in the vapor
80. uch as Visual C or Visual BASIC The interfaces provided for Excel Mathcad and 1 2 3 intercept these error numbers and return appropriate Excel Mathcad or 1 2 3 error values This is done to avoid inadvertent use of an error value in a cell equation ERR_OUTOFRANGE 1002 Out of Range The input values represent a state point that is outside of the Gas pressure or temperature range ERR_NOTAVAILABLE 1003 Not Available The property requested is not available at these conditions ERR_NOTDEFINED 1004 Not Defined The property requested is not defined at these conditions ERR NOSAT 1100 No Saturation The temperature of the gas is above the saturation temperature of the water vapor ERR_H20 1200 H20 composition error The H20 component is less than 0 ERR_N2 1300 N2 composition error The Nitrogen component is less than 0 ERR_O2 1400 O2 composition error The Oxygen component is less than 0 ERR_CO2 1500 CO2 composition error The CO2 component is less than 0 ERR_AR 1600 AR composition error The Argon component is less than 0 ERR MF 1800 mole fraction error None of the gas components entered were greater than 0 ERR_THIGH 2000 Temperature Too High Gas will accept a maximum temperature of 2000 deg K Gas for Windows Version 3 2 User s Manual Appendix Il Gas Error Codes Page 74 ERR TLOW 2100 Temperature Too Low Gas will accept a minimum temperature of 180 deg K
81. unction is GasPXD which returns the Dew Point or Dry Bulb Temperature at which the gas becomes saturated based on the amount of water vapor in the gas composition The function GasPTXHs calculates the enthalpy of the gas mixture saturated with water at a given pressure and temperature It is equivalent to calling the GasPTXW function to get the saturated humidity ratio and then calling the GasPTXH function with the calculated humidity ratio A similar function GasPTXSs is provided for entropy 2 2 1 Valid Operating Range The Gas functions are generally valid over a temperature range from 180 K 136 F to 2000 K 3140 F and at pressures up to 5 0 MPa 725 psia The functions detect requests for calculations outside that range and return an error value The valid ranges of some functions depend on the amount of water vapor in the gas composition Those functions may therefore return out of range errors even though pressure Gas for Windows Version 3 2 User s Manual Page 4 Chapter 2 Using the Gas Property Functions Page 5 and temperature are within the ranges cited above When an out of range or invalid set of inputs is used the add in functions i e Excel or 1 2 3 add ins simply return error values VALUE or NUM But DeskTop Gas produces informative error messages DeskTop Gas can be used in conjunction with the add ins to develop an understanding of what causes error values in your spreadsheet calculations
82. urns the specific enthalpy of the moist gas Arguments pressure temperature MNS Xoz Xan Xcoz XH20 unit set Return Value specific enthalpy Examples Description is a value representing the absolute total pressure of the gas in units consistent with the selected unit set is a value representing the dry bulb temperature of the gas in units consistent with the selected unit set the gas composition N2 O2 Ar CO2 H20 of the gas Zus Kos Xar and Xco2 are entered as mole fractions of the dry gas with Xuso entered as a humidity ratio All of the five arguments must be entered in order even if any are zero If 32 is added to the unit set all X values are entered as mole fractions of the wet gas If 64 is added to the unit set mass fractions are substituted wherever mole fractions are required 0 or ENG 1 or SI 2 or EngG 3 or SIF 4 or SIK 5 or MET 6 or METF Description is the specific enthalpy per mass of dry gas in units consistent with the selected unit set and ASHRAE reference point If 16 is added to the unit set output is per mass of wet gas If 8 is added to the unit set enthalpy is referenced to absolute zero temperature Examples 2 _ _ gt _ EE P 14 696 psia T 100 deg F N2 0 740285 O2 0 198589 Ar 0 008855 CO2 0 000298 H20 0 051973 GasPTXH 14 696 100 0 740285 0 198589 0 008855 0 000298 0 051973 48 59 657 Btu lbm of wet gas Gas
83. ve arguments must be entered in order even if any are zero If 32 is added to the unit set all X values are entered as mole fractions of the wet gas If 64 is added to the unit set mass fractions are substituted wherever mole fractions are required 0 or ENG 1 or SI 2 or EngG 3 or SIF 4 or SIK 5 or MET 6 or METF Description is a value representing the temperature in units consistent with the selected unit set below which the moisture in the gas begins to condense Examples P 14 696 psia N2 0 740285 O2 0 198589 Ar 0 008855 CO2 0 000298 H20 0 051973 GasPXD 14 696 0 740285 0 198589 0 008855 0 000298 0 051973 48 92 68 deg F Gas for Windows Version 3 2 User s Manual Appendix Gas Detailed Function Listing Page 62 GasXW GasXWI XN2 Xo2 Xan Xco2 XHzo unit set returns the humidity ratio of the moist gas Arguments Aus Xoz Xan Xco2 XH20 unit set Return Value humidity ratio Description the gas composition N2 O2 Ar CO2 H20 of the gas Zus Kos Xar and Xco2 are entered as mole fractions of the dry gas with Xuso entered as a humidity ratio All of the five arguments must be entered in order even if any are zero If 32 is added to the unit set all X values are entered as mole fractions of the wet gas If 64 is added to the unit set mass fractions are substituted wherever mole fractions are required 0 or ENG 1 or SI 2 or EngG
84. were measured on a computer using a 1 8 GHz Pentium IV processor Calculation times will vary depending on your particular computer Note that the recalculation options selected will also affect perceived calculation time 5 2 ACCURACY OF CALCULATIONS Thermodynamic properties for the pure gases calculated by Gas have been checked against the values published by NBS 1 and ASME 6 for water vapor As shown on Tables 1 through 20 the calculated values show excellent agreement with the source data throughout most of the valid range Some small differences can be observed at low temperatures and high pressures This is due to the limitations of using a third order virial equation of state Gas for Windows Version 3 2 User s Manual Chapter 5 Speed and Accuracy Page 32 There is little published data on the properties of mixed gases One method to illustrate the accuracy of the mixing equations is to compare the results of Gas to data for dry air which is a mixture of Nitrogen Oxygen Argon and a small amount of Carbon Dioxide Tables 21 through 24 show the comparison with air for the thermodynamic properties As with the pure components small errors can be observed at low temperatures and high pressures due to the limitations of the model The tables show some differences in enthalpy entropy and specific heat occurring at 850 K and growing with temperature This initially was thought to be attributed to dissociation but this was dis
85. y Hy x Ay Hy H Hi x H X T R KE E T x EN N where where n coefficient of viscosity of pure gas component i 2M M TKM M 0 0 ET N 266 93 10 7 T kT e reduced temperature o amp T parameters in the potential function characteristic of 1 2 interaction x mole fraction of component i M molecular weight of component i A 022 OUD Q integrals for calculating the transport coefficients for the Leonard Jones 6 12 potential Once we have the viscosity of the non polar gas mixture we can use the equations for a polar non polar mixture The equation for viscosity of a binary mixture is as follows Gas for Windows Version 3 2 User s Manual Chapter 4 Theoretical Basis of Gas Functions Page 28 AR 1 Z l n where 7 viscosity of the mixture 2 2 x 2X xX x Ge EE H w w X N 1 ew Ny 2 2 2 Y YA de GEE LM M New Es M ni 12 7 5 TM m AMM Ann TM M M M Z 4 x _ 8 42x x g ay Te Mew 1 22 M 7 5 g M amp 4M M D D M 7 viscosity of dry gas mixture at the specified temperature 1 viscosity of water vapor at the specified temperature 2 Fis T gw and C1 266 93E 7 O potential function parameter for mixture adjusted for one polar molecule M weighted average molecular mass of the dry gas mixture To correct for pressure we use the method of Chung et al as

@Gas User`s Manual - Techware Engineering

Contents

Download Pdf Manuals

Related Search

Related Contents