This document is not a departmental publication. Version 2.1 User`s
Contents
1. 2 0 08 19 7 246 0 32 3 724 7 9 3 0 16 38 0 234 5 61 9 682 4 0 4 0 20 32 5 161 5 55 6 452 2 9 lt 5 0 2 16 1 76 1 51 2 189 12 6 6 0 21 6 6 31 1 62 0 63 18 0 lt lt lt lt 7 0 22 4 7 21 7 56 9 37 19 0 lt lt 8 0 23 8 1 35 7 56 0 72 17 6 4 9 0 21 9 2 44 3 42 1 96 15 9 4 42 4 4 4 2 4 4 4 10 0 14 13 3 98 5 31 0 252 10 0 4 11 0 07 14 3 194 5 23 6 557 0 6 4 12 0 06 15 5 262 4 25 4 770 6 8 4 24 222 2 2 24 222 4 2 4 4 4 YEAR 0 12 200 7 1727 7 541 0 4853 THE AVERAGE COLLECTION EFFICIENCY OVER THE YEAR 15 0 37 THE YEARLY SOLAR CONTRIBUTION PER SQUARE METRE IS 2 01 GJ M2 YR THE MAX VALUE OF FR IS 02. VENTAIR Version 2 1 User s Manual November 1982 Assistance and Information K Ford Design Aids Engineer Solar Programs Office Sir Charles Tupper Building Riverside Drive Ottawa 0M2 613 998 3641 tt This document is not a departmental publication Do not cite as a reference or catalogue in a library User Responsibility Users are responsible for the validity of the information generated by VENTAIR Version 2 1 Consequently the program should not be used by those who do not comprehend the technical field to which this program applies Neither Public Works Canada nor any person acting on behalf of the department makes any warrenty or assumes any responsibility for accuracy completeness or usefulness of any information generated by this program 6 7 8 9 TABLE OF CONTENTS INTRODUCTION 1 1 Introduction to Ventilation Air Systems 1 2 Introduction to Industrial Process Air Heating Systems THE VENTAIR 2 COMPUTER PROGRAM 2 1 System Configuration 2 2 System Operating Strategy 2 3 Tutorial Session SYSTEM INPUT PARAMETERS 3 1 Definition of Input Parameters 3 2 Weather Data and Map DESCRIPTION OF PROGRAM OUTPUT PROGRAM ALGORITHM 5 1 Overview of Program Operation 5 2 Algorithm for the Calculation of Fp 5 3 Algorithm to Process Weather Data PROGRAM STRUCTURE REFERENCES INPUT DATA WORK SHEET NOMENCLATURE FIGURE 1 SYSTEM SCHEMATIC FIGURE 2 VENTA
3. 202205 2352355325 tug dep do Jes diee eg Dea ou Das Dag sg Do u02s02 ENTER THE 24 VALUES FOR VENTILATION RATE M3 S FOR DAY 2 057055025072 202202 05785 rbe sbo Oss Un OS ENTER THE 24 VALUES FOR VENTILATION RATE M3 S FOR DAY 3 0s te Tes 0 0 0 0 0 0 0 0 0 ENTER THE 24 VALUES FOR VENTILATION RATE M3 S FOR DAY 4 0550220 502 055024 02502502 02 0 202502502 0s 20200 70e 507502004 202 ENTER THE 24 VALUES FOR VENTILATION RATE M3 S FOR DAY 5 4 d ta 1o ts 1e 1s 1s 1e Ve Ta ta bo Ta 1a 4 de Lh to Tar Te 441 ENTER THE 24 VALUES FOR VENTILATION RATE 13 5 FOR DAY 6 0 0 50 05 0 pHs ler la lo c6 560 Us 6a pbe 70a 8 ENTER THE 24 VALUES FOR VENTILATION RATE M3 S FOR DAY 7 0 0 0 0 0 0 9 9 9 9 9 9 9 9 9 99 9 9 9 9 9 9 0 0 Note that the hourly values can be separated by a blank or a comma and need not be all on one line 15 3 SYSTEM INPUT PARAMETERS The following sections describe the parameters used in the VENTAIR 2 computer program The user must ensure that the parameters are in the appro priate units 3 1 Definition of Input Parameters SOLAR RADIATION SECTION COLLECTOR SLOPE DEG The angle that the collector is tilted from the horizontal in degrees Range O to 90 COLLECTOR AZIMUTH ANGLE SOUTH O DEG The number of degrees
4. Y N n DO YOU WISH TO CHANGE SYSTEMS SECTION Y N n DO YOU WISH TO CHANGE VENTILATION RATE SCHEDULE SECTION Y N n When all input values are correct the program will ask for the title of the run The title has no effect on the program calculations but merely serves as a method for distinguishing between computer runs The title can be up to 64 characters in length including blanks on a single line ENTER TITLE OF RUN sapple run After the title has been entered the simulation starts The program first prints out the input data and the run title 3k oc Xo koc c aoo c KRG RK EER KEK REE EEA VENTAIR 2 1 SOLAR PREHEATED VENTILATION AIE PROGRAM TO MODEL USE OF SOLAR COLLECTORS TO PREHEAT VENTILATION AIR ak dk co c c boe EE ER EERE KEK oc ooo c ox kc koc c xoc EK eoo oce e oo xbox eoXetoke xe oec SAMPLE RUN INPUT DATA COLLECTOR SLOPE DEG oid ew cewecw sew eee we 15 00 LOCATION LATITUDE DEG SSeS ace ese COLLECTOR TEST DATA EDTA o us eu Wee ene FRUL 22 5 5 2 710 COLLECTOR TRANS ABSORP PEODUCT ee eee se 0 860 APERATURE TO GROSS AREA RATIO e eec e ee ee 0 872 COLLECTOR TEST FLCW RATE M3 S M2 cee 0 010 CHANNEL HEIGHT 0 025 FLOW LENGTH TEST CONDITIONS M 10 000 SYSTEMS DATA
5. GROSS COLLECTCR AREA 82 ccccccccccccconcenve 100 0 MAXIMUM SOLAR SYSTEM FLOW BATE M3 S 1 50 BUILDING OR PROCESS TEMPERATURE C 20 00 ARRAY FLOW LENGTH lt lt lt lt lt lt oo 10 00 VENTILATION RATE SCHEDULE M3 S DAY OF THE WEEK HOUR 1 2 3 4 5 6 7 0 3 00 3 00 3 00 3 00 3 00 3 00 3 00 1 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 3 00 WEAN Ut 10 10 3 00 3 00 3 00 3 00 3 00 3 00 3 00 11 3 00 3 00 3 00 3 00 3 00 3 00 3 00 12 3 00 3 00 3 00 3 00 3 00 3 00 3 00 13 3 00 3 00 3 00 3 00 3 00 3 00 3 00 14 3 00 3 00 3 00 3 00 3 00 3 00 3 00 15 3 00 3 00 3 00 3 00 3 00 3 00 3 00 16 3 00 3 00 3 00 3 00 3 00 3 00 3 00 17 3 00 3 00 3 00 3 00 3 00 3 00 3 00 18 3 00 3 00 3 00 3 00 3 00 3 00 3 00 19 3 00 3 00 3 00 3 00 3 00 3 00 3 00 20 3 00 3 00 3 00 3 00 3 00 3 00 3 00 21 3 00 3 00 3 00 3 00 3 00 3 00 3 00 22 3 00 3 00 3 00 3 00 3 00 3 00 3 00 23 3 00 3 00 3 00 3 00 3 00 3 00 3 00 The program performs two data checks one to see if the collector data is reasonable two to see if the systems data is reasonable If either check fails the program prints a warn
6. H is H 1 605 s c where p is the ground reflectivity The total solar radiation on the tilted surface Hr is the sum of the beam diffuse and reflected solar radiation components Hourly values of total solar radiation on a tilted surface ambient temperature day number and hour number are written to the scratch file When all the data has been processed and written to the scratch file the file is rewound to be ready for the system simulation 36 6 PROGRAM STRUCTURE The program structure is described in this section Only those individuals interested in modifying the program need read this section The program flow chart is shown in Figure 4 The program consists of a mainline and four subroutines 1 MAINLINE main program for file unit number allocation and calling of subroutines ii INPUT interactive subroutine for user input of data and printing of input data iii WEATH subroutine for converting measured horizontal solar radiation to the tilted surface iv VENT subroutine to calculate system performance on an hourly basis v FRCALC subroutine to calculate the collector heat removal factor FR for a given set of meteorological conditions and flow rate Four file definitions must be made before the program can be run Terminal Unit 8 is the device used for data input The program will send all questions and prompts to this device Printer Unit 6 is the device that receives the output
7. i e a printer If a send and receive printer is being used unit 6 and 8 will be the same device Weather Data Unit 9 is the file containing the TRNSYS compatible weather data The data must be written in the format 2X I2 2X I2 2X I2 F3 1 13 F6 1 and contain month number day number hour number ground reflectivity ambient temperature C and solar radiation on a horizontal surface W m Processed Data Unit 10 is the file that is created by the program containing the solar radiation on the tilted surface and ambient temperature Figure 4 VENTAIR 2 Program Structure Start MAINLINE FRCALC BAR VENT Output to Printer Weather Data INPUT WEATH Processed Data 37 38 1 2 3 REFERENCES Morton B and Carpenter S Use of Air based Solar Collectors to Preheat Ventilation Air 1981 Solar Energy Society of Canada Inc Conference Montreal 1981 Duffie and Beckman Solar Engineering of Thermal Processes John Wiley and Sons New York 1980 Orgill J F and Hollands K G T Solar Energy Vol 19 No 2 Correlation Equation for Hourly Diffuse Radiation on a Horizontal Surface Temps R C and Coulson K L Solar Energy Vol 19 No 2 Solar Radiation Incident upon Slopes of Different Orientation Klucher T M Solar Energy Vol 23 No 2 Evaluation of Models to Predict Insulation on Tilted Surfaces 39 8 INP
8. 1 55699 1 84013 if 0 35 s 0 75 Hy 1 0 248857 K H if 0 0 lt s 0 35 where H is the measured hourly solar radiation is the ratio of measured solar radiation to the extraterrestrial solar radiation H Hox The beam radiation Hp is simply the total measured solar radiation minus the diffuse radiation H H H b d The next step is to calculate the ratio of beam radiation on the tilted surface to that on the horizontal surface Rp cos 64 cos e where cos ex is the cosine of the angle of incidence of beam radiation between the beam and the normal to the surface COS sin sin cos s cos 6 cos cos s cos w cos sin sin s cos y cos w cos 6 sin s sin y sin w y is the azimuth angle measured from south east is positive west is negative Thus the beam solar radiation on the tilted surface is bT Rp b H The diffuse solar radiation component on the tilted surface is estimated using the radiation view factor from the collector to the sky with correction factors for non uniform distribution of diffuse radiation 35 The correction factors for anisotropic diffuse radiation are taken from Temps and Coulson 4 and Klucher 5 The resulting equation is Hat qe oy 1 F sin s 2 1 F cos eq sin 3 Ha where 1 The reflected solar radiation on the tilted surface
9. 43 7 45 4 Year 1971 1974 1971 1971 1975 1971 1971 1971 1971 1971 1971 1975 1971 1971 1971 1971 1971 1971 1966 1971 1971 1971 1971 1971 1971 Solar Rad Derived Measured D M M D e oc mm Montreal Sept Iles Quebec Sherbrooke Riviere du Loop Bagotville Val D Or Fredericton Charlo Chatham Moncton St John Charlottetown Truro Halifax Sydney Yarmouth St John s Gander Stephenville Goose Que Que Que Que Que Que Que N B N B N B N B N B P E I N S N S N S N S Nfld Nfld Nfid Nfld 45 5 50 2 46 8 45 4 47 8 48 3 48 0 45 9 48 0 47 0 46 1 45 3 46 3 45 4 44 7 46 2 43 8 47 6 49 0 48 5 53 3 1971 1974 1971 1971 1971 1971 1971 1971 1971 1971 1971 1971 1971 1971 1971 1971 1971 1971 1971 1971 1971 c O O O x vO x 21 22 4 DESCRIPTION OF PROGRAM OUTPUT At the conclusion of each simulated month results are printed The results are an estimate of the performance of a properly designed and installed system Because the system has no thermal storage it is possible to adjust the system performance according to the number of days of operation For example the solar contribution of a 5 day on 2 day off ventilation schedule would be 5 7 of a 7 day on schedule The
10. Figure 3 rd Back Insulation Schematic of Fibre Matrix Solar Collector Glazings Fibre Matrix oE 31 h is the radiative heattransfer coefficient between the fibre matrix and the lower glazing Because of the nature of the fibre matrix h is a weighted average of the value of h for each layer bf fibres with the top layer having a weighting _of 1 and the bottom layer having a weighting of 0 integrating the values for h over the depth of the matrix can be approximated by hr t 276 where hey o T T2 1 222 h o T r2 2 4 T Teo T5 1 222 fo T is the temperature of the top of the fibre matrix 1 is the temperature of the lower glazing The average fibre matrix plate temperature can be calculated by Tplate a Tem Qu U where Uo is the fibre matrix to air heat transfer coefficient is the average fluid temperature fm Estimating Uo for fibre matrix collectors is much more difficult than for parallel plate collectors The reference used for these equations is Kays W and London A L Compact Heat Exchangers Second Edition McGraw Hill New York 1964 pg 129 For fibre matrices Kays and London give equations of the form Acn 273 U x m Cp Re Pr A c where Pr is the Prandtl number where x and y are constants dependent on the type and shape of the matrix For a similar type of fibre matrix Kays and
11. London give Xx 1 3 y 0 45 By knowing the average fibre matrix diameter and the fibre matrix mass the ratio of heat transfer to collector area can be calculated For the Amherst collector 80 LH 5 3 Algorithm to Process Weather Data Most Canadian weather stations measure only total solar radiation on a horizontal surface Most solar collectors however are tilted toward the sun to increase the incident solar radiation The program determines hourly values of total solar radiation beam diffuse and reflected on a tilted surface and stores the values in a scratch file The algorithm for converting horizontal solar radiation to tilted solar radiation is similar to the method used in Solar Engineering of Thermal Processes by Duffie and Beckman 2 In order to estimate the solar radiation on a tilted surface it is necessary to split the total measured horizontal solar radiation into its two components beam and diffuse It is possible to estimate the amount of diffuse solar radiation from the ratio of the measured solar radiation to the extraterrestrial solar radiation If this ratio is low then the solar radiation must be mostly diffuse if this ratio is high the solar radiation must be mostly beam When the beam and diffuse solar radiation components are known standard geometric relations can be used to estimate the solar radiation components on a tilted surface When estimating solar radiation on a tilted surface a
12. heat the building i e by supplying ventilation air at a temperature higher than the building temperature However this is a much more difficult control problem requiring zone heat control for ventilated and unventilated areas Control feedback to the solar ventilation system would be necessary in the ventilated areas to prevent overheating Such a control strategy is not considered applicable for space heating 2 3 Tutorial Session This section describes how to use the VENTAIR 2 computer program A full description of the input parameters is given in Section 3 and program output in Section 4 When you have successfully signed on to your account and accessed the program the computer will respond with the header 00 8 0 e too sek ox oc dco o e 3 Se sette ot EEE ER EE RE EE EE KE AK EEE KEKE KEKE VENTAIR 2 1 AN HOUR BY HOUR COMPUTER PROGRAM TO MODEL USE OF SOLAR COLLECTORS TO PREHEAT BUILDING VENTILATICN AIR 3 OR CREE RO OR Ro do do eo d do dookec ek a okoeotekokoloec tek E z Ei E E E i E e eee The program will prompt the user for values of input parameters for four sections solar radiation collector systems and ventilation rate schedule as follows SOLAR RADIATION SECTION ENTER COLLECTOR SLOPE DEG 45 ENTER COLLECTOR AZIMUTH ANGLE SOUTH 0 DEG 0 0 ENTER LOCATION LATITUDE DEG 45 PROCESSING WEATHER DATA ELEASE BE PATIENT COLLECTOR SECTION THE PROGKAM
13. hour of the week VENTILATION RATE SCHEDULE SECTION ENTER LOAD SCHEDULE TYPE 1 CONSTANT VENTILATION RATE 2 TWO VENTILATION RATES PER DAY 3 VENTILATION RATE DIFFERENT FOR EACH HOUR 2 ENTER DAY VENTILATION RATE 3 ENTER NIGHT 0 ENTER HOUR 9 ENTER HOUR 17 ENTER HOUR 9 ENTER HOUR 17 ENTER HOUR 9 ENTER HOUR 17 ENTER HOUR 9 ENTER HOUR 17 ENTER HOUR 9 ENTER HOUR 17 ENTER HOUR 0 ENTER HOUR 0 ENTER HOUB 0 ENTER HOUE 0 VENTILATION RATE 0 0 0 lt 0 0 0 0 0 0 0 0 0 gt 0 23 23 23 23 23 23 23 23 23 23 23 23 23 23 THAT THAT THAT THAT THAT THAT THAT THAT THAT THAT THAT THAT THAT THAT DAY DAY DAY DAY DAY DAY DAY DAY DAY DAY DAY DAY DAY DAY N 3 S 1835 RATE STARTS FOR DAY 1 RATE STOPS FOR DAY 1 RATE STARTS FOR DAY 2 RATE STOPS FOR DAY 2 RATE STARTS FOR DAY 3 RATE STOPS FOR DAY 3 RATE STARTS FOR DAY 4 RATE STOPS FOR DAY 4 RATE STARTS FOR DAY 5 RATE STOPS FOR DAY 5 RATE STARTS FOR DAY 6 RATE STOPS FOR DAY 6 RATE STARTS FOR DAY 7 RATE STOPS FOR DAY 7 14 VENTILATION RATE SCHEDULE SECTION ENTER LOAD SCHEDULE TYPE 1 CONSTANT VENTILATION RATE 2 TWO VENTILATION RATES PER DAY 3 VENTILATION RATE DIFFERENT FOR EACH HOUR 3 ENTER THE 24 VALUES FOR VENTILATION RATE M3 S FOR DAY 1 0220210
14. that the collector is oriented off due south east is positive west is negative Range 90 to 90 LOCATION LATITUDE DEG The latitude of the location that is being simulated in degrees See Section 3 2 for values COLLECTOR SECTION The program has default values for four solar collectors The user must specify a number between one and four to select the appropriate collector If the number 0 not the letter 0 is selected the user may input collector parameters of other collectors The program checks these parameters to ensure consistency The program will not run if the input parameters are not realistic The input parameters required if the number 0 is selected are described below These parameters apply only to a parallel plate solar collector and not a fibre matrix collector 16 COLLECTOR FRTA The of the collector as determined from certified performance testing based on gross collector area Available from collector data sheets COLLECTOR FRUL W M 2 C The FpU of the collector as determined from certified performance testing in W m C based on gross collector area Available from collector data sheets TRANSMISSION ABSORPTION PRODUCT The effective of the collector This can be estimated as 1 01 times for a single glazed collector where is the glazing solar transmission and a is absorber solar absorptivity RATIO OF COLLECTOR APERTURE TO GROSS AREA The ratio of the collector aperture a
15. third component is introduced reflected radiation Reflected radiation can be estimated from the beam radiation and the ground albedo or reflectivity 33 The program equations and execution procedure are given below At the start of each day the solar constant and the earth s solar declination are calculated The solar constant is given by Sc 4871 0 1 0 33 cos 2 365 in KJ hr m where N is the day number Jan 1 is 1 The earth s declination is given by amp 23 45 24 Sin 24 284 N in radians 360 360 365 These values are assumed constant for each day All other calculations are made on an hourly basis The first step is to read the measured weather values from the data file For each hour the weather data file contains six values in the following 1 month number 1 12 2 day number 1 31 3 hour number 1 24 4 ground reflectivity 5 solar radiation on a horizontal surface in Watts m 6 ambient temperature in ec The extraterrestrial solar radiation on a horizontal surface is calculated by Hs S 605 92 where cos e is cosine of the zenith angle angle between the beam and the vertical cos 62 cos 4 cos 6 605 w sing sins is the latitude of the location w is the hour angle The diffuse solar radiation Hy can be estimated using a correlation by Orgill and Hollands 3 0 1769 H if 0 75 K x t d T His
16. 825 OCCURING WHEN SOLAR RAD IS 863 4 W M2 AND AMB TEMP IS 30 0 C The program then asks the user if another run is to be made DO YOU WISH TO CONTINUE Y N ARE ALL THE VALUES CORRECT Y N DO YOU WISH TO CHANGE SOLAR RADIATION SECTION Y N n DO YOU WISH TO CHANGE COLLECTOR SECTION Y N Y 12 To simulate the performance of the system in a different city the user must answer N and restart with the VENTAIR c mmand and the name of the new city The previous example was for one of the PUSH approved collectors 1f another collector is to be used the program will prompt for the collector characteristics COLLECTOR SECTION THE PROGRAM HAS DATA FOR 4 SOLAR CCLLECTORS AMHERST 200 SOLARTECH SOLAIR WATERSHED A100 NARROW CHANNEL WATERSHED A100 WIDE CHANNEL EWN SELECT THE COLLECIOR TO BE SIMULATED USE ZERC FOR A COILECTCR NOT LISTED ABOVE HOWEVER IT MUST BE A PARALLEL PLATE COLLECTOR NOT A FIBRE MATRIX COLLECTOR 0 ENTER COLLECTOR 0 60 ENTER COLLECTOR FRUL W M 2 C 4 0 ENTER TRANSMISSION ABSORPTICN PRODUCT 0 9 ENTER RATIO OF COLLECTOR APERATURE 10 GROSS AREA 0 9 ENTER COLLECTOR TEST FLOW RATE M 3 M 2 S 0 01 ENTER COLLECTOR PLOW CHANNEL HEIGHT M 0 05 ENTER COLLECTOR PLOW CHANNEL LENGTH M 2 have two ventilation rates per day or a different ventilation rate for each 13 In addition to selecting a constant ventilation rate the user can
17. Calculate solar contribution Figure 2 VENTAIR 2 Program Flow Chart cont d ef Calculate building inlet temperature Tin Is Tai lt desired building temperature Add Qc Q to previous values Has all the N weather data been used Go To 2 Output system performance Do you wish Go To 1 to continue STOP 1 Fg for Parllel Plate Solar Collectors FR is given by Fn m Cp 1 exp F U Cp UL where F U C Ui All of the variables are constant except for m mass flow rate per 9 unit area and Uo the total plate to fluid heat transfer coefficient m is given each hour by the air flow rate schedule thus a new value of Uo must be calculated for each hour Uo depends on the collector design The equations for Uo given below were taken from Hollands K G T and Shewen E C Journal of Solar Energy Engineering Vol 103 No 4 November 1981 Optimization of Flow Passage Geometry for Air Heating Plate Type Solar Collectors Uo n hot i hof f hy i hoe where hy is the radiative heat transfer coefficient between the upper and lower absorber plates if we assume that the inside of the air channel is painted black i o T T5 Ty 1 222 where and T are the temperatures of the upper and lower absorber 1 2 plates h f is the convective heat transfer coefficient between the plate PY and the air stream h Nu k 2 b p
18. HAS DATA FOR 4 SOLAR CCLLECTORS 3 AMHERST 200 SOLARTECH SOLAIR WATERSHED A100 NARROW CHANNEL WATERSHED A100 WIDE CHANNEL ht SELECT THE COLLECTOR TO BE SIMULATED USE ZERO FOR A COLLECTOR NOT LISTED ABOVE HOWEVER IT MUST BE A PARALLEL PLATE COLLECTCR NOT A FIBRE MATRIX COLLECTOR 3 SYSTEMS SECTION ENTER REQUIRED BUILDING OR PROCESS TEMPERATURE C ZMIER GROSS COLLECICR AREA M 2 MAXIMUM ALLOWABLE SOLAR SYSTEM FLOW RATE M 3 S tires ARRAY FLOW PATH LENGTH MO VENTILATION RATE SCHEDULE SECTION ENTER LOAD SCHEDULE TYPE 1 CONSTANT VENTILATION RATE 2 TWO VENTILATION RATES PER DAY 3 VENTILATION RATE DIFFERENT FOR EACH HOUR 1 ENTER BUILDING VENTILATION BATE M 3 S 3 0 G see page 18 for description When all of the input data has been entered the user is able to modify any of the sections The program will prompt the user with questions to respond type Y for yes and N for no DO YOU WISH TO CONTINUE Y N y ABE ALL THE VALUES CORRECT Y N Y If the user types N in response to DO YOU WISH TO CONTINUE the program will stop and the session will be over If the user answers N to ARE ALL THE VALUES CORRECT the program will ask which section s are to be modified If the solar radiation section is changed the weather data will be reprocessed DO YOU WISH TO CHANGE SOLAR RADIATION SECTION Y N n DO YOU WISH TO CHANGE COLLECTOR SECTION
19. IR 2 PROGRAM FLOW CHART FIGURE 3 SCHEMATIC OF FIBRE MATRIX SOLAR COLLECTOR FIGURE 4 VENTAIR 2 PROGRAM STRUCTURE Page m C CO CO hore 15 18 22 24 24 25 32 36 38 39 40 26 27 30 37 1 INTRODUCTION The VENTAIR 2 computer program was developed by Enermodal Engineering Limited to simulate the performance of air based solar collectors used in the preheating of industrial process or building ventilation air The program can accept data of all PUSH approved air based collectors Amherst 200 Solartech Solair and Watershed A100 and any other parallel plate air based collector VENTAIR 2 is the only computer program capable of simulating solar preheating of process or ventilation air Performance calculations use a one hour time step to ensure maximum accuracy An important restriction however on the use of the program is that the air demand must be constant over the hour A system not applicable to the VENTAIR 2 program for example is a bathroom ventilation system operating by a light switch or short duration timer The VENTAIR 2 computer program will provide an accurate estimate of thermal performance of solar preheated process or ventilation air systems provided that the user supplies system parameters within the program limitations AI users should read and understand this manual before using the program 1 1 Introduction to Ventilation Air Systems In many buildings a high rate of change of ve
20. LATION RATE SCHEDULE SECTION The air flow rate can be varied for every hour of a 7 day cycle The user can input the air flow rate in one of three ways 1 constant air flow rate all week 2 two air flow rates per day 3 a different air flow rate for each hour Process or ventilation rates selected should be the total air flow rate into the building even if this flow rate does not all go through the collectors 3 2 Weather Data At present there is weather data for 46 cities that can be used by the program These cities are tabulated below The solar radiation data as supplied by Atmospheric Environment Service is of two types derived or measured Measured data is as recorded by their monitoring equipment with missing data estimated from the previous day s values Derived data is predicted by using other meteorological data such as rainfall cloud cover etc City Victoria Prince George Vancouver Summerland Frobisher Bay Resolute Edmonton Medicine Hat Uranium City Swift Current Saskatoon Churchill Brandon Winnipeg The Pas Thunder Bay Sault Ste Marie Sudbury Kapuskasing Kingston Muskoka Windsor London Toronto Ottawa Province B C B C B C B C N W T N W T Alta Alta Sask Sask Sask Man Man Man Man Latitude Deg 48 7 53 9 49 2 49 6 63 8 74 7 53 6 50 0 59 6 50 3 52 2 58 8 49 9 49 9 53 8 48 4 46 5 46 5 49 4 44 2 45 0 42 3 43 0
21. UT DATA WORK SHEET VENTAIR 2 Input Data Solar Radiation Data Collector Slope degrees Collector Azimuth degrees Location Latitude degrees Collector Test Data Select from 1 to 4 for default collector parameters or if zero is selected enter FRU W m C Transmission Absorption Product Aperture to Gross Area Ratio Collector Test Flow Rate m s m Channel Height b m Flow Length Test Conditions Systems Data Collector Area m Maximum Solar System Flow Rate m s Building or Process Temperature C Array Flow Length Process or Ventilation Rate Schedule 1 Constant Air Flow Rate all week 2 Two Air Flow Rates per day 3 Air Flow Rate different for each hour 168 values 40 hpf 9 NOMENCLATURE total collector area m area of one collector m surface area of fibre matrix m collector channel height m specific heat KJ kg C Uo Uy d u collector heat removal factor collector transmission absorption coefficient collector heat loss coefficient W m C measured hourly solar radiation KJ hr m beam hourly solar radiation KJ hr m beam hourly solar radiation on a tilted surface KJ hr m diffuse hourly solar radiation KJ hr m diffuse hourly solar radiation on a tilted surface KJ hr m extraterrestrial hourly solar radiation KJ hr m plate to fluid convective heat transfer coefficient radiative heat t
22. altion air this value would be the thermostat set point For process air this value would be the process air temperature There is no upper limit on the process temperature although a high process temperature will result in a low fraction solar GROSS COLLECTOR AREA M 2 The gross collector area in square metres MAXIMUM ALLOWABLE SOLAR SYSTEM FLOW RATE weg s The maximum flow rate that can be drawn by the solar collectors in m s This value would normally be equal to the maximum ventilation rate however in cases of high ventilation rate where a small collector area is used the maximum collector flow rate would be less than the venti lation rate A reduced value is used because at high flow rates the incremental fan power consumption exceeds the incremental solar contribution The user shouldcheck with the collector manufacturer for the maximum allowable collector flow rate Typically the maximum collector flow rate should result in a static pressure loss of less than 250 Pa D 1m s 2119 cfm 18 Note that this parameter is a total system flow and not a per unit collector area flow ARRAY FLOW PATH LENGTH M This is the total distance or length that the air stream is in contact with the absorber In most cases this value would be the length of the collector in the flow direction times the number of collectors in series For short path collectors see the note under COLLECTOR FLOW CHANNEL LENGTH in Section 3 1 PROCESS OR VENTI
23. conditioning equipment before entering the space 2 All Solar Heating If the ambient air temperature drops below the building or process temperature some air would flow through the collectors This is accomplished by partially opening damper 1 and partially closing damper 2 see Figure 1 Flow would continue to be diverted until the supply air temperature reaches the building or process temperature In this operation all the heat necessary to bring the ambient air temperature up to the building or process temperature is supplied by the solar collectors 3 Partial Solar Heating As the ambient temperature continues to decrease more air is taken through the collectors and less through the direct fresh air intake A point will be reached when the collectors are operating at maximum air flow damper 1 fully open damper 2 fully closed and the building supply air temperature T1 is less than the required temperature In this case additional heating is supplied by the heating coil It should be noted that solar collectors have a maximum flow rate where the incremental solar heat gain is less than the incremental fan energy consumption Thus in many designs with the maximum flow rate of air flowing through the collectors some air would be supplied through the direct fresh air intake in order to meet the required ventilation rate In Mode 2 all the available solar heat has not been used Theoretically this heat could be used to
24. f where k is the conductivity of air b is the spacing between the upper and lower absorber plates Nu is the Nusselt number 29 for Re 2000 Reynolds number Nu 5 385 0 148 Re b n L n is the number of air flow passage channels typically equal to 1 L is the collector flow path length for 2000 Re 10000 1 2 0 471 Nu 0 00044 Re 9 37 Re for 10000 Re x 100000 0 74 0 74 Nu 0 03 Re 0 788 Re b n L where Re 2 m L u if Re is greater than 100000 the program sets Re equal to 100000 ii Fp for Fibre Matrix Collectors see Figure 3 The estimation of Fe for fibre matrix collectors requires a different formulation for Fg Fp can be thought of as the ratio of the actual useful energy to the useful energy if the absorber plate were at the fluid inlet temperature Tei For a ventilation collector FR is pce UM ae Ti equo ave Try tal U Te Tei 1 where is the average temperature that the collector loses heat at This temperature is normally the average plate temperature however a fibre matrix collector has inlet air blowing across the lower glazing thus loses heat from a lower temperature For a fibre matrix collector Tiye is Tave E Tplate E hof Tg hy i hoe where h f is the convective heat transfer coefficient between the lower P glazing and the air stream Air Flow In Solar Radiation 1 T fi
25. g load are greater than zero Fp is calculated for that hour s flow rate and meteorological conditions The equations for Fp are given in Section 5 2 The maximum solar contribution is calculated with the equation Qs Fp ta I A The inlet temperature to the building Tin is calculated based on Q Tin Ta C If this temperature is greater than the desired temperature Thg then Qs is made equal to Qi The values of Qs and Q are added to the previous values and the program moves to the next hour At the end of each simulated month the monthly totals of solar contri bution and heating load are printed full description of the output is given in Section 4 5 2 Algorithm for the Calculation of Fg lt lt lt Two separate algorithms are used for the calculation of Fe one for parallel plate solar collectors and one for fibre matrix solar collectors It is important to note that a correction on FR for the number of collectors in series is not necessary provided that the mass flow per unit area is kept constant 26 Figure 2 VENTAIR 2 Program Flow Chart Input Variables Calculate solar radiation on a Is solar radiation on a tilted sur face available tilted surface Are collector parameters and flow rates reasonable Read solar radia tion and ambient temperature for next hour Calculate ventila tion heating load Q Calculate FR
26. he daily air flow schedule is very short this value will be low regardless of the collector performance curve YEARLY SOLAR CONTRIBUTION PER SQUARE METRE The yearly solar contribution divided by the collector area good application of a solar preheated ventilation air system would have a value of over 1 0 GJ m yr MAX VALUE OF FR The maximum value of the collector heat removal factor Fg for any hour during the simulation If this value is below the test value of FR the system may not be well designed i e collector flow rate too low or collector area too large 24 5 PROGRAM ALGORITHM 5 1 Overview of Program Operation The VENTAIR 2 computer program calculates the performance of solar preheated process or ventilation air systems on an hour by hour basis The basic assumption of the program is that for the purpose of calculating performance all variables including solar radiation ambient temperature and building ventilation rate can be considered constant for each hour Thus if the building ventilation rate varies widely within a given hour the VENTAIR 2 program is not applicable An example of a system where VENTAIR 2 is not applicable is a bathroom ventilation system operated by a light switch or short duration timer The program calculation flow chart is shown in Figure 2 The first step in the program is the input of the input parameters in an interactive manner Section 3 gives a full description of the input para
27. ing and returns the user to the input section The three warnings are 14 THE MAXIMUM FLOW RATE TO COLLECTOR AREA IS 0 001 M3 N2 S THE MINIMUM ALLOWABLE VALUE IS 0 002 THE COLLECTOR AREA IS TOO SHALL OR THE MAXIMUM FLOW RATE TOO LAEGE 2 THE NAIIMUM FLOW RATE TO COLLECTOR AREA IS 0 100 M3 H2 s THE MAXIMUM ALLOWABLE VALUE IS 0 05 THE COLLECTOR AREA IS TOO LARGE OR THE MAXIMUM FLOW RATE TOO SMALL 34 THE MAIINUM FLOW RATE TO COLLECTOR AREA IS 0 010 483 1215 WITH THE GIVEN TEST CONDITIONS THE COLLECTOR HAD AN FR OF 0 77 UNDER THE SAME CONDITIONS THE PROGRAN CALCULATES AN FR OF 0 53 Then the program will print PROGRAM CANNOT ACCURATELY SIMULATE SYSTEM SITH THE PARAMETERS CHOSEN PLEASE RE CHECK INPUT DATA If the data checks are successful the system is simulated and the results are printed on a monthly basis with a yearly summary at the end WHEN TESTED THE COLLECTOR HAD AN FR OF 0 77 UNDER THE SAME CONDITIONS THE PROGRAM CALCULATES AN FR OF 0 77 11 Scc t e EEE E E i E ke ex PERFORMANCE PRELICTION 3k d xo c KEKE EKER AKER ERAS EEE EEE FRACTION SOLAR TOTAL SOLAR DEGREE AMBIENT MONTH SOLAR CONTRIB LOAD RAD DAYS TEMP GJ 63 GJ C DAY DEG C 4 1 0 07 22 7 322 4 37 0 960 13 0
28. meters After all the parameters have been entered the program calculates the collector heat removal factor for the test values of flow rate and flow path length using the method given in Section 5 2 This value is compared to the value of FR found from the collector term The two values are printed at the terminal At the test condition the calculated value of Fp will be either higher or lower than the test value If the difference between the values if greater than 15 the program prints a warning and returns to the input mode A check is also made on the collector flow rate If the collector flow rate per unit area is not reasonable minimum value 0 002 m m s maximum value 0 05 m m s the program prints a warning and returns to the input mode Each time new values are given to the variables in the solar radiation section the solar radiation on a tilted surface is recalculated The algorithm 25 for performing this calculation is given in Section 5 3 When the solar radiation and the input parameters are correct the program begins the simulation at January Ist A new value of solar radiation and ambient temperature is read for each simulated hour and the process or ventilation air heating load is calculated Q If the load is zero the program goes to the next hour If the solar radiation is zero the load is added to the previous load values and the program moves to the next hour If the solar radiation and heatin
29. more energy per square metre than a conventional solar space heating system see reference 1 If a solar contribution significantly higher than 352 is required thermal storage should be considered although the increased cost may not be justified A side effect of eliminating the storage unit is the simplification of system control and ductwork 2 2 System Operating Strategy The system has three modes of operation excluding complete shut down These modes are summarized in Figure 1 and described below 1 No Solar Heating If the ambient air temperature is greater than the required building Collector Blower Collector Panels T Face and Solar Heated Bypass Damper 5 se Building Fresh Air Supply Air 9 Sensor Direct Fresh Air 5 Ti Heating LI D ouis t 4 Ee EIE ZONE gt Two stage Control Unit Tbg is the desired inlet temperature to the building or process Sequence of Operation Damper 1 Damper 2 Tamb MD1 MD2 Collector Blower MD3 Heating Coil Ti OFF bypass OFF Tog N b 0 ypass FF Thg bypass l and coti ON Thg or process air temperature no heating of the air is required In order to eliminate an unnecessarily high cooling load all air enters the direct fresh air intake bypassing the solar collectors The air bypasses the heating coil and is handled by conventional air
30. ntilation air is necessary for the health of the occupants or proper operating of equipment Such buildings include hospitals vehicle maintenance garages indoor swimming pools and commercia kitchens The volumes of air involved are often quite large 6 air changes hour and correspondingly large quantities of energy are required to raise the air temperature to the building temperature This air is normally heated by steam coils or electric resistance heaters reduce energy consumption heat recovery equipment can be used to transfer some of the heat from the exhaust air to the fresh air Heat recovery equipment however has several limitations The equipment suffers from frost build up in sub freezing conditions fouling from kitchen grease and requires modifications if the exhaust air contains toxic chemicals The installation of this equipment can be expensive in retrofit situations if return air duct work must be added Use of air based solar collectors to preheat ventilation air has been proposed as a parallel application of a viable alternative to heat recovery equipment in many applications In making a decision to use this type of system it is necessary to estimate the yearly thermal performance The VENTAIR 2 computer program was designed specifically to assist the designer in evaluating the system performance of solar preheated ventilation air systems 1 2 Introduction to Industrial Process Air Heating Systems Many ind
31. output values are MONTH The month of the simulation January is 1 December is 12 FRACTION SOLAR The fraction of the total heating load that is met by the solar heating system This value can be misleading if it is not taken in context with the ventilation or process air rate schedule Because there is no thermal storage the solar heating system cannot meet any of the night time heating demand Thus a building that ventilates evenly 24 hours a day could never have a fraction solar over 0 4 Whereas a building that ventilates for only one hour per day at noon could have a fraction solar of over 0 70 The first system however is probably the more cost effective SOLAR CONTRIB GJ The amount of solar energy that is used to heat the process or venti lation air Alternatively this value can be thought of as the reduction in auxiliary energy to heat the air TOTAL LOAD GJ The energy required to heat the process or ventilation air if there were no solar heating system 23 SOLAR RAD GJ The total solar radiation incident on the gross collector area regardless of whether the system is operating DEGREE DAYS C DAY The number of degree days based on 18 C This is a measure of how cold the location is AMBIENT TEMP DEG C The average ambient or outdoor temperature for the time period AVERAGE COLLECTION EFFICIENCY OVER THE YEAR The yearly solar contribution divided by the solar radiation It is important to note that if t
32. ransfer coefficient reflected hourly solar radiation KJ hr m total incident solar radiation KJ hr m clearness index length of collector in flow direction m mass flow rate kg hr number of air flow passage channels day number of the year Nusselt Number lt bg 2 10 a lt lt lt 41 air heating load KJ hr maximum solar heating contribution KJ hr useful heat collected by the collector KJ hr ratio of beam radiation on tilted surface to horizontal surface Reynolds Number collector slope solar constant temperature of upper and lower plates of the air channel C ambient temperature C average temperature that collector losses heat from 50 temperature of building or process C collector fluid inlet temperature C average collector fluid temperature C collector fluid outlet temperature C inlet temperature to the building C average temperature of the collector absorber plate 50 collector heat loss coefficient W m C total plate to fluid heat transfer coefficient W m 9 C matrix constant matrix constant solar absorptivity p density kg m solar declination Stefan Boltzmann constant azimuth angle hour angle latitude E transmission absorption product 3 14159 ta effective transmission absorption product absolute viscosity
33. rea i e window area to the gross area Typically this value is usually close to 0 9 actual values can be obtained from collector data sheets COLLECTOR TEST FLOW RATE M 3 M 2 S The flow rate per unit area used when the collector parameters and F U were determined It is important to note that the units R RL are M s per square metre of gross collector area This parameter is ususally close to 0 01 m m s COLLECTOR FLOW CHANNEL HEIGHT M The spacing between the upper and lower absorber plates in metres For a curved upper absorber use the average spacing Range 0 01 to 0 1 In general decreasing the flow channel height increases the collector Fp although this will result in a higher collector pressure drop 17 COLLECTOR FLOW CHANNEL LENGTH TEST CONDITIONS M The distance or length that the air stream is in contact with the absorber plate In most collectors this will be the length of collector in the flow direction times the number of collectors in series when tested In some cases collectors are designed so that the contact length is much shorter than the collector such as the overlapped glass plate Increasing the flow channel length increases the flow rate through each collector This results in an improved Fp but at increased collector pressure drop SYSTEMS SECTION REQUIRED BUILDING OR PROCESS TEMPERATURE C The desired temperature of air entering the building or process in Celsius For venti
34. ustrial processes require large volumes of air for drying and or heating Such processes include paint drying food drying combustion air preheating and sterilization drying of bottles and cans The VENTAIR 2 computer program can also be used to simulate solar preheating of these processes provided that the air flow rate is constant over each hour If the flow rate is dependent on the relative humidity and or ambient temperature the VENTAIR 2 computer program is not suitable 2 THE VENTAIR 2 COMPUTER PROGRAM 2 1 System Configuration In a conventional make up air unit fresh outside air is taken into the building by a roof top fan A bypass damper automatically adjusts the fraction of the intake air that passes through the heating coil to main tain the required inlet air temperature Exhaust air is expelled to the out doors by a separate system Figure 1 shows a system schematic for a typical solar preheated process or ventilation air system This system differs from conventional solar space heating systems in two important areas First the inlet air to the collector is the outside or ambient air as opposed to the building air This means that the collector will operate at a lower temperature and a higher efficiency Second because the solar energy is delivered immediately to the heating load there is no need for thermal storage If the solar heating contri bution of the total heating load is below 352 this system can deliver
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