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1. CryoSoft 2013 The time integration starts at the last time stored on file co currentHX store as specified below and proceeds to the new EndTime with the prescribed OutputStep EndTime 50 0 OutputStep 5 0 Log output and results are appended to the existing files during the restart LogFile co currentHX log StorageFile co currentHX store end Post processing command file The following is an example of the sequence of commands necessary to generate of print outs and plots using the post processor FLOWERPOST co currentHxX post Post processing sequence for the parallel current heat exchanger simulation A PostScript output file co currentHX ps is generated containing all plots Define the file where results are stored StorageFile co currentHxX store Define the file for Postscript R and printed output PostScriptFile co currentHX ps OutputFile co currentHxX out The number of plots per page can be set to 1 2 3 4 or 6 set plotsperpage 3 Select the results of the simulation at the times closest to those below all following plots are as f x the selected times are parameters select time 0 1 1 10 Plot various quantities as f x selecting the quantity first the component s next plot temperature junction 1 junction 2 plot pressure junction 1 junction 2 plot velocity junction 1 junction 2 The stop command terminates parsing the post processing session is finished sto
2. CryoSoft 2013 48 CHAPTER 7 Troubleshooting and Errors Error messages are reported to the output ASCII log file and to the standard output The form of a typical error report is the following ERROR in procedure lt procedure name gt lt error message gt called by lt calling procure gt at position lt n gt called by lt calling procure gt at position lt m gt where lt procedure name gt is the name of the routine where the error occurred and lt error message gt reports a short description of the error situation This line is followed by the trace of the lt calling procedure gt up to the main program In case of queries about error conditions please take care to report error messages completely including the calling trace Errors can be generated at four different levels in the code e input parsing and syntax errors e data consistency errors e runtime errors e internal consistency errors Input parsing errors Input parsing and syntax errors are detected during the interpretation of the input file They indicate that the variable naming the command syntax or the type and number of numerical data in the input file are incorrect Verify syntax in the input file in this case Data consistency errors Data consistency errors are detected when input data are not coherent among themselves and would result in a model that cannot be analyzed Typical cases are selection of incompatible options or input data o
3. Structure and syntax The post processing command file is read by the post processor interpreter of FLOWERPOST This parses and analyzes the syntax and the grammar of the various entries In general the file contains a series of commands that are executed in sequence during a post processing session The structure and content of the post processing command file is similar to that of the input file already described in Chapter 4 In particular the following rules and conventions apply the identifier of a variable and the corresponding value s can appear at any position on the line they can carry on to several lines and must be separated by blanks or tabs the interpretation is case insensitive abbreviations of the keys are not allowed acharacter in any position of the command line indicates that the remainder of the line must be considered as a comment If the is the first character in a line then the whole line is ignored Parsing of the input file is finished as soon as an end of file or the stop command are found At this point the post processor completes all pending print outs and plots and closes the session For sample input files see Chapter 3 Commands reference Post processing commands In this section we report the list of the postprocessing commands and their meaning in alphabetical order The keywords identifying commands and options are given in Courier Parameters and values for the commands are
4. EXTERNAL ROUTINES Linking external routines Calling protocol Pipe Friction Factor vdo O an oo 10 11 12 13 18 22 41 41 41 45 45 45 46 O CryoSoft 2013 Valve Head Loss Factor Volume Heating Pipe Heating Pipe Heat Transfer Coefficient TROUBLESHOOTING AND ERRORS Input parsing errors Data consistency errors Runtime errors Internal consistency errors REFERENCES 46 47 47 47 48 48 48 48 49 50 O CryoSoft 2013 Roadmap 5 Roadmap Before you start This manual is the reference user s guide for FLOWER and its post processor FLOWERPOST Throughout this manual we assume that the reader is familiar with the physics and engineering issues that are associated with the design and analysis of a cryogenic pipework consisting of both passive pipes heat exchangers valves and active pumps turbines components Details on the physics modeling that is at the basis of the program are given in 1 2 and 3 We strongly suggest that the reader consults and familiarizes with these references before using this manual How to use this manual This manual is structured as follows Chapter 1 contains a brief and general introduction on the modeling principle and solution methods available 7 Chapter 2 gives basic information on the installation explains how to start a FLOWER run and launch the post processor FLOWERPOST on a UNIX workstation Chapter 3 contains c
5. seconds of simulation Flag triggering a restart If this key is present in this block FLOWER reads the content of the specified StorageFile until the last stored time is found The simulation begins then from this time Storage of results continues on StorageFile appended All input will be ignored except for EndTime LogFile OutputStep and TimeStep Start time for the beginning of the simulation Flag for the method used to estimate the time step based on the time integration error and the requested Tolerance Possible values none no estimate of the time step is performed The time step taken is equal to the MinimumStep specified smooth the time step is increased decreased smoothly by means of fixed percentage change default A StepEstimate smooth requires that an ErrorEstimate method is provided change or halving power the time step is increased decreased scaling the ratio of the time integration error to the required Tolerance using the order of accuracy of the time integration method A StepEstimate power requires that an ErrorEstimate method is provided change or halving Binary storage file name This file contains the results stored at the user s specified times and is used for restarts or post processing If not given the default file name is flower store Flag for the selection of the time integration method Possible values CryoSoft 2013 Chapter4 Input Reference 37 EulerBackward Eu
6. you will need to compile them and link them to the standard part of the code to produce a customized version of the executable of FLOWER For this purpose you can use the standard makefile CryoSoft etc flower make that can be copied and modified Once more we strongly suggest that you modify only a copy of the standard makefile Refer to the installation guide 4 for more details on the use of the makefiles compilation and link editing of the program Calling protocol The following sections describe the calling protocol for the External Routines For clarity we have subdivided the description in sections that are either associated with the type of function or with the type of component involved The convention followed for the definition of the FORTRAN type of variables is the same as described in Chapter 4 O CryoSoft 2013 46 The External Routines for FLOWER are defined as FORTRAN functions The function returns a single real or integer value that must be computed by the user within the routine All parameters passed to the function must be regarded as input parameters and cannot be modified Note FORTRAN unit numbers above 50 are reserved by the CryoSoft library for internal use and should not be allocated for read write operations Any allocation or use of units above 50 can result in I O errors or malfunctions Pipe Friction Factor real function userFriction ij 1X Reynol FrictionFactor Returns the
7. can be regarded in first approximation as an assembly of active and passive components forming an hydraulic network Ina FLOWER model we consider the network as composed of e interconnected junctions where the flow can be steady state or transient Junctions can be of different type passive e g a pipe or a valve or active e g a pump or a turbine e volume nodes with perfect mixing of helium and zero flow representing buffers and manifolds In the model definition the junctions always interconnect volume nodes Volumes however can have negligible size so that the result is a direct interconnection of two or more junctions in the same point The junction definitions are based on the following types included in the model 1 D flow pipes including full compressible flow and propagation delay and waves e valves with concentrated head loss and isenthalpic flow pumps volumetric or centrifugal with isentropic flow e turbines also with isentropic flow In addition the model considers thermal links among 1 D flow pipes as e g in the case of heat exchange between parallel flows among 1 D pipes and volumes as would be the case for heat exchange between a pipe submerged in a bath and among volumes Figure 1 shows a schematic representation of a possible hydraulic network We refer to 3 for the details of the model implemented Here we recall only the main assumptions and limitations that affect the user CryoSoft 2
8. connection 1 2 ThermalResistance 10 0 End Begin Link 2 thermal link for the heat exchanger pipe type JV connection 4 6 ThermalResistance 0 1 End CryoSoft 2013 Chapter 3 Case Studies 25 Post processing command file As for the previous cases we report below an example of the sequence of commands necessary to generate plots using the post processor FLOWERPOST loop regulated post Post processing sequence for the run of the simple loop example as specified in the input file loop regulated input The output produced is a PostScript file loop regulated ps and an ASCII file with printed results loop regulated out StorageFile loop regulated store PostScriptFile loop regulated ps OutputFile loop regulated out set color on plot temperature volume 1 volume 2 volume 3 volume 4 volume 5 volume 6 volume 7 plot pressure volume 1 volume 2 volume 3 volume 4 volume 5 volume 6 volume 7 plot density volume 1 volume 2 volume 3 volume 4 volume 5 volume 6 volume 7 plot enthalpy volume 1 volume 2 volume 3 volume 4 volume 5 volume 6 volume 7 select x 0 plot massflow junction 1 junction 2 plot massflow junction 3 junction 4 junction 5 junction 6 plot massflow junction 7 select time 0 1 1 10 100 plot temperature junction 1 junction 2 plot pressure junction 1 junction 2 plot velocity junction 1 junction 2 plot massflow junction 1 junction 2 plot temperature junction 4 plot pressure junction 4 pl
9. for the couple formed by a given junction type and input parameter means that the corresponding input value must exist and must be greater than zero A entry means that the parameter value in input must be one of the predefined keywords see the Input Variable Reference section Default values are taken if the parameter definition is missing in the input file CryoSoft 2013 34 Links The links block determines the coupling among volumes and junctions Note All components must be defined before defining their mutual links This means that the links block must come after the volume and junction blocks in the input file A parsing error is generated if this is not the case Variable Type Units Meaning Connection ThermalResistance Type I1 O Array of 2 elements containing the volume junctions indices defining the link For a junction of type JJ the first and the second entries are the numbers of the first and the second junctions linked For a link of type JV the first entry is the junction linked to the volume specified by the second entry For a link type VV the first and the second entries are the numbers of the first and the second volumes linked R K W m Thermal resistance This thermal resistance is added to the thermal resistance of the boundary layer of the flow in the case of links with a junction Flag describing the link coupling Possible values JJ junction to junction c
10. friction factor fama 16 0 079 Re Bia Heat transfer coefficient The heat transfer coefficient h is defined as a function of the Reynolds and Prandtl numbers Re and Pr through the Nusselt number Nu Different pre programmed available correlations can be chosen in input among the standard definitions reported in 6 The default definition is the Dittus Boelter correlation that reads Nu 0 023 Re Pr where the Nusselt number is given by noes k and k is the thermal conductivity of the fluid Loss coefficient in valves The loss coefficient for valves is defined such that the pressure drop is given by Ap 2 amp ov where amp is assumed to be a constant The relation between the loss factor amp and the commonly used coefficient K is the following 2 A 6 5x10 v where A is the cross section of the valve CryoSoft 2013 40 Compressor characteristic The compressor characteristic is approximated as Ap Y Mo 1 2p for Ap gt 0 m APo Mo for Ap s0 where the massflow 71 is delivered when there is no pressure difference at the extreme of the pumps and Apo is the maximum pressure head that can be sustained with zero mass flow The characteristic is plotted below as compared to that of a volumetric pump volumetric pump compressor Pr Pi Px Pr APo CryoSoft 2013 Chapter5 Post processing Language Reference 41 CHAPTER 5 Post processing Language Reference
11. friction factor of a junction representing a pipe Called if Friction user for a junction of type SSPipe or Cpipe The calculation is performed at all nodes of the junction identified by their nodal coordinate See earlier for the definition of the pressure drop induced by the friction factor Parameter Type Units Meaning ij I Junction number x R m Node coordinate from inlet Reynol R Reynolds number of the flow FrictionFactor R O reference friction factor as from input Valve Head Loss Factor real function userCsi ij time p T rdpr imdot csi Returns the head loss factor of a junction representing a valve Called if Friction user for a junction of type ControlValve CheckValve BurstDisk or Turbine See earlier for a definition of the pressure drop induced by the loss factor Parameter Type Units Meaning ij I Junction number time R s Simulation time p R Pa Array of 2 elements containing the inlet and outlet pressure in the junction T R K Array of 2 elements containing the inlet and outlet temperature in the junction dpr R Pa Pressure drop along the junction at time time inlet to outlet mdot R Kg s massflow in the junction at time time csi R reference head loss factor as from input CryoSoft 2013 Chapter 6 External Routines 47 Volume Heating real function userVHeating iv time p Ao 1q0 rtau0 Returns the heating power deposition W in a volume Cal
12. given in italic Note The selection of the items to plot or to print is done identifying first the target i e quantity to be plotted printed and then the support i e the component over which the quantity is defined Each support must be followed by its identification number coherent with the input simulation file e g Volume 2 for the second volume component defined in the input for the simulation with FLOWER NewPage Force a new plot page to be generated CryoSoft 2013 42 OutputFile name Set the name of the file for printed output generated with the command Print The default file name for printed output is flowerpost out The file name can be changed only before the first printed output is generated The command is ignored if a printed output has already been generated on another file or on the default file Plot target support support Support Generate n plot frames of target for the specified support s as a function of time or space according to the selection done see the Select command Example plot pressure junction 1 junction 2 Plot target support vs target support Plot target of support versus target of support at all times or space positions selected see the Select command Example plot velocity junction 1 vs velocity junction 2 PostScriptFile name Set the name of the file containing Postscript output The default file name for printed output is lowerpost ps The file
13. indicates comments to the input that are ignored by the input parser CryoSoft 2013 Chapter 3 Case Studies 13 Parallel flow heat exchanger Physical definition of the problem This case shows how to model heat exchange between two pipes where helium is flowing at different temperatures The direction of the flow inlet to outlet is the same for the two pipes The flow is driven by a pressure difference of 0 05 bar between the inlet and outlet manifolds of the pipes These manifolds are assumed to have a very large ideally infinite volumes The inlet temperature for the first pipe is 300 K while for the second pipe it is 320 K Heat exchange takes place between the two pipes through a thermal resistance that is obtained as the series of the following thermal resistances e thermal resistance associated with heat convection between the helium flow in the first pipe and the pipe wall e equivalent thermal resistance of the pipe wall and any intermediate thermal barrier as specified in the thermal link definition the value assumed is 0 1 K W m distributed along the whole length of the pipes and e thermal resistance associated with heat convection between the pipe wall and the helium flow in the second pipe Note that while the thermal resistance of the pipe walls is given in input the heat transfer from the flow to the pipe wall through the thermal boundary layer is computed automatically for the two flows As shown be
14. input file is needed both for a start up run and a restart run Similarly post processing of FLOWER results using the post processor FLOWERPOST requires an input file with a sequence of commands that select results print and plot them We refer to this file as the post processing command file In this Chapter we give examples of input files and post processing command files to deal with practical modeling situations The case studies given here are intended to guide the user from the formulation of a problem to its modeling the creation of the input file for the case running the case and finally the generation of the results For obvious reasons they are of limited complexity and are intended as examples to illustrate minimum capability of the program More complex situations can obviously be modeled taking the following case studies as starting points and evolving or combining them Refer to Chapter 2 on how to run the examples described here with FLOWER and how to generate results and plots with FLOWERPOST Note All input files and post processing command files for the case studies discussed in this manual are provided with the standard installation They are located in the directory CryoSoft xample flower code_x x where x x stands for the version you received In the following sections we use the Courier font to reproduce the content of the input files while text in italic starting with a semicolon in the input files
15. same quantities print temperature junction 1 junction 2 print pressure junction 1 junction 2 print velocity junction 1 junction 2 The stop command terminates parsing the post processing session is finished stop Results Two files are generated running the post processor FLOWERPOST with the commands described abovein the file counter currentHX post the PostScript output counter currentHX ps and the ASCII output counter currentHX out The plots below show the first page in the PostScript output counter currentHX ps As requested in the commands file the plots are the pressure temperature and velocity distributions along the junctions 1 and 2 at selected times CryoSoft 2013 Chapter 3 Case Studies 21 FLOWER 4 4 7 12 2013 10 08 29 counter currentHX junction 1 junction 1 _ junction 1 SSS junction 2 SSeS junction 2 SSS 25 junction 2 i TTT TTT TTT wg Ry A 1 00E 01 s we A E 1 00E 01 s 2 1 00E 01 s B 1 00E 00 s 7 F B 4 00E 00 s a J 1 00E 00 s gt 1 00E 01 s 7 H C 00E 01 s y 4 1 00E 01 s s A T H J i a a BE 4 Q l at 4 E 2 K J HE 2 gt o sf 1 gt am 3 E J a H a E J v o n 5 J 8 E S E J 3 st J amp a ek J gt lt E J e EEEE gadah N g 5 10 0 5 10 X m X m Page 1 Figure 5 Temperature pressure and flow velocity along the two pipes of the counter flow heat exchanger at different times Note the pressure gradient in op
16. the standard input file Specifically the user can e modify the dependence of geometry waveforms and material properties on space time and solution variables beyond the standard models implemented using External Routines that can be statically linked to the program segments through a compilation step that produces a customized version of the code See Chapter 6 for documentation on External Routines e change parametrically the behavior of the External Routines by making use of Variables that are read by the code input parser and can be accessed at run time using the Variables library See Chapter 4 for details on the syntax to be adopted for the Variables input block e couple to other programs of the CryoSoft suite through the multi tasking code manager SUPERMAGNET This allows to augment the physics span of the simulation domain to include thermal networks e g heat exchange in a coil hydraulic networks e g proximity cryogenics or electrical circuits e g magnet protection CryoSoft 2013 Chapter2 Installing and Running FLOWER 9 CHAPTER 2 Installing and Running FLOWER Platforms FLOWER and its post processor FLOWERPOST are provided as a package developed for running under UNIX or UNIX like e g Linux operating system The reason is that they require computer intensive calculations orderly file management and little interactivity At the time when this manual is written the platform where FLOWER has been deve
17. the volumes Junction define the general properties of the junctions Links define the links among components Simulation define the simulation parameters Variables define user variables for use in routines and functions The content of a block is a series of assignations of a set of values to a generic variable VariableName VariableName must be chosen among the set of keywords described in the following sections The structure and content of the input file must comply with the following rules and conventions the identifier of a variable and the corresponding value s can appear at any position on the line they can carry on to several lines and must be separated by blanks or tabs the interpretation is case insensitive abbreviations of the keys are not allowed a character in any position of the command line indicates that the remainder of the line must be considered as a comment If the is the first character in a line then the whole line is ignored the variables in the block are read sequentially and are checked at read in time For this reason the order of precedence of the variables must be respected whenever a value is CryoSoft 2013 28 needed to proceed with the interpretation of a block i e the total number of volumes or junctions must be available before reading the single volume junction blocks The same BlockName can appear more than once in a file repeated variable assignation
18. 013 Introduction 7 e the flow of helium is in single phase but can be both in supercritical or superfluid state Superfluid counter flow heat exchange is automatically activated when the state is below the lambda transition e all volumes manifolds are assumed to have perfect mixing of the incoming flows and are therefore identified by a single pressure and temperature e the flow in all connections pipes valves pumps and turbines is assumed to be compressible but steady state i e all wave propagation delays are neglected through these components The only exception is the compressible flow pipe element that model the flow using the full set of compressible flow equations e pumps are always providing a massflow either independent on the pressure difference from inlet to outlet as is the case for volumetric pumps or depending on the pressure difference as is the case for compressors In both cases the pump is assumed to act ideally i e the fluid undergoes an isentropic transformation from inlet to outlet e turbines act on the flow as concentrated hydraulic resistances in which the fluid undergoes an isentropic state transformation With these hypotheses the network can be solved using mass and energy balances at the volumes manifolds and momentum and energy balances in steady state in the incompressible flow connections The compressible flow pipe is based on the complete solution of transient mass momentum and energy balance
19. End Definition of the first pipe connecting volumes 1 and 2 defined previously The wetted perimeter enters in the definition of the total thermal resistance from the flow in pipe I to pipe 2 and is therefore required when linking junctions to other junctions or volumes Begin Junction 1 type Cpipe connection 1 2 L 10 0 A 3 14e 4 Dh 1 0e 2 N 300 WP 3 14e 2 End The second pipe connecting volumes 3 and 4 has the same characteristics as pipe 1 Begin Junction 2 type Cpipe connection 3 4 L 10 0 A 3 14e 4 Dh 1 0e 2 N 300 WP 3 14e 2 End The link block defines the thermal connections of elemen In this case the thermal link is between junctions JJ type linking pipes 1 and 2 Begin Link 1 type JJ connection 1 2 ThermalResistance 0 1 End At this point the input definition is complete and execution starts Input file for the restart run To proceed with the simulation for a longer time than 25 s the EndTime specified in the start up run we use the restart feature of FLOWER Below we give the step by step definition of the input file for the restart of the simulation with a reduced time resolution in the storage of results co currentHX restart In case of restart only the simulation parameters are needed All other parameters are taken from the storage file generated during the previous run Begin Simulation The presence of the Restart keyword is necessary to trigger a restart run Restart
20. User s Guide Version 44 December 2013 FLOWER Hydraulic Network Simulation DISCLAIMER Even though CryoSoft has carefully reviewed this manual CRYOSOFT MAKES NO WARRANTY EITHER EXPRESSED OR IMPLIED WITH RESPECT TO THIS MANUAL ITS QUALITY ACCURACY MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE AS A RESULT THIS MANUAL IS PROVIDED AS IS AND YOU THE PURCHASER ARE ASSUMING THE ENTIRE RISK AS TO ITS QUALITY AND ACCURACY IN NO EVENT WILL CRYOSOFT BE LIABLE FOR DIRECT INDIRECT SPECIAL INCIDENTAL OR CONSEQUENTIAL DAMAGES RESULTING FROM ANY DEFECT OR INACCURACY IN THIS MANUAL even if advised of the possibility of such damages Copyright 1997 2009 2013 by CryoSoft CryoSoft 2013 Contents ROADMAP Before you start How to use this manual INTRODUCTION What is FLOWER A FLOWER model Model Solution Post processing User Flexibility and Further Extensions INSTALLING AND RUNNING FLOWER Platforms Installation How to run FLOWER How to run FLOWERPOST Customization CASE STUDIES Parallel flow heat exchanger Counter flow heat exchanger Regulated circulation loop INPUT REFERENCE Structure and syntax Input variables reference Volume Junction Links Simulation Variables Standard definitions Friction factor Heat transfer coefficient Loss coefficient in valves Compressor characteristic POST PROCESSING LANGUAGE REFERENCE Structure and syntax Commands reference
21. ase studies that the reader should use to familiarize with the operation and features of the program Chapter 4 contains additional information on the preparation of the input and the meaning of the input variables Chapter 5 describes the details of the post processing command language Chapter 6 describes the External Routines that can be used for advanced use These routines can be linked to the standard code to provide powerful customization Chapter 7 deals with troubleshooting and error messages Chapter 8 gives the references and a general bibliography for documentation Beginners to FLOWER should read chapters 1 2 and 3 in sequence They will make occasional cross reference to chapters 4 and 5 for detailed information Experienced users will use chapters 4 5 and 6 for daily operation Chapter 7 is designed as an indexed glossary for error messages and associated actions CryoSoft 2013 CHAPTER Introduction What is FLOWER FLOWER is a model for the thermo hydraulic simulation of an arbitrary user defined assembly of manifolds pipes heat exchangers valves turbines and pumps the hydraulic network It provides pressure temperature and massflow conditions throughout the network and as a function of time It is aimed at the simulation of the integrated response of the proximity cryogenics of a whole installation including the pipework of a magnetic system A FLOWER model A typical cryogenic system
22. ative x Begin Junction 2 type Cpipe connection 4 3 L 10 0 A 3 14e 4 Dh 1 0e 2 N 300 WP 3 14e 2 End The thermal link between junctions acts as a distributed thermal resistance between points at the same x in the junction Begin Link 1 type JJ connection 1 2 ThermalResistance 0 05 End CryoSoft 2013 Post processing command file The following is an example of the sequence of commands necessary to generate of print outs and plots using the post processor FLOWERPOST counter currentHX post Post processing sequence for the counter current heat exchanger simulation A PostScript output file counter currentHX ps is generated containing all plots and an ASCII file counter current output containing tables of selected data Define the file where results are stored StorageFile counter currentHX store Define the file for Postscript R and printed output PostScriptFile counter currentHX ps OutputFile counter currentHX out The number of plots per page can be set to 1 2 3 4 or 6 set plotsperpage 3 Select the results of the simulation at the times closest to those below All following plots are as f x the selected times are parameters select time 0 1 1 10 Plot various quantities as f x selecting the quantity first the component next plot temperature junction 1 junction 2 plot pressure junction 1 junction 2 plot velocity junction 1 junction 2 Produce a printout of the
23. ber must follow the keyword Volume Variable Type Units Meaning Heating C Heating type Possible values none no heating default user user defined through the function userVHeating see Chapter 6 window the heating is defined as constant equal to q in an interval 0 lt t lt Tau and zero outside this interval See the end of this chapter for more details p R Pa Initial pressure in the volume q R W Heating power only used in the case of a heated volume T R K Initial temperature of the volume Tauq R s Heating time only used in the case of a heated volume v R m Volume CryoSoft 2013 Chapter4 Input Reference 29 Junction The Junction block defines all components interconnecting volumes and is used to assign their geometric and operating characteristics The junction number must follow the keyword Junction Variable Type Units Meaning A R Connection I csi R csiModel C Dh R Dp R Dp0 R fModel C m m Pa Flow cross section of the junction Array of 2 elements containing the volume indices defining the junction The first volume is connected to the eftmost location of the junction x 0 while the second volume is connected to the rightmost location of the junction x L In the case of oriented junctions i e pumps or check valves and burst disks the first volume is assumed to be the inlet while the second is the outlet of
24. d Begin Volume 2 outlet manifold V 1 0e 6 P 5e5 T 4 5 End Begin Volume 3 node between pump and heat exchanger pipe V 1 0e 6 P 5e5 T 4 5 End Begin Volume 4 node between heat exchanger pipe and valve V 1 0e 6 P 5e5 T 4 5 End Begin Volume 5 node between valve and feeder relief V 1 0e 6 P 5e5 T 4 5 End Begin Volume 6 heat exchanger volume artificially large V 1 0 P 2e5 T 4 5 End Begin Volume 7 pressure regulation buffer artificially large V 1 0 P 5e5 T 4 5 End CryoSoft 2013 24 Begin Junction 1 first flow pipe type Cpipe connection 1 2 L 10 0 A 3 14e 6 Dh 1 0e 3 N 250 WP 3 14e 3 Heating window Q 1 0 tauQ 100 0 heated pipe End Begin Junction 2 second flow pipe type Cpipe connection 1 2 L 10 0 A 3 14e 6 Dh 1 0e 3 N 250 WP 3 14e 3 End Begin Junction 3 volumetric pump type pump connection 2 3 L 1 0 A 3 14e 4 m0 1 0e 3 End Begin Junction 4 heat exchanger pipe type Cpipe connection 3 4 L 25 0 A 1 0e 4 Dh 1 0e 2 N 250 WP 3 14e 2 End Begin Junction 5 control valve with constant head loss type ControlValve connection 4 5 L 1 0 A 3 14e 4 csi 10 0 End Begin Junction 6 feeder pipe to inlet manifold type SSpipe connection 5 1 L 1 0 A 3 14e 4 Dh 1 0e 2 End Begin Junction 7 pressure control valve opening when the Dp gt I bar type CheckValve connection 5 7 L 1 0 A 1 0e 4 csi 1 0e6 Dp 1 0e 5 End Begin Link 1 thermal link between thw two pipes type JJ
25. delled The fluid name can be one of the following predefined standard names Helium Single phase He in any state including superfluid Nitrogen Single phase N gt Only one fluid can be defined for the network to avoid inconsistencies caused by flow mixing HOExtrapolate C Switch for higher order extrapolation of the results of a time step The order of accuracy of the time stepping method chosen is used to extrapolate the solution to a higher order Possible values none_ no higher order extrapolation applied default on at each time step the solution is extrapolated using the result of a time step and of two subsequent time steps of halved magnitude The higher order extrapolation can significantly increase CPU time and in pathological situations it leads to numerical instabilities CryoSoft 2013 36 Junctions Links LogFile MaximumStep MinimumStep OutputStep Restart StartTime StepEstimate StorageFile TimeMethod s s s s Total number of junctions Total number of links Log file name This file contains the echo of the input and the log of the run including error messages If not given the default log file name is flower log Maximum time step allowed during adaptive time integration Minimum time step allowed during adaptive time integration Time step for storage of the results The results are written to the output binary file every OutputStep
26. e compressor The massflow depends quadratically on the pressure head see the end of this chapter for more details default user the characteristics of the compressor is defined through a user routine Note The feature of a user defined pressure head characteristics is not yet active in this version of FLOWER Unpredictable results will be generated if the input file contains this keyword selection q R W m Power input along the pipe used only for Heating type window or user Tauq R s Heating time only used for Heating type window or user Type C Junction type See 3 for details on the models The input parameters that are needed to define the junction characteristics is reported in table 1 Possible values for the type of junction are SSPipe steady state flow pipe compressible flow but no wave propagation CPipe compressible flow pipe full set of compressible flow equations including wave propagation ControlValve control valve resulting in a localised pressure loss CryoSoft 2013 32 WP CheckValve BurstDisk Pump Compressor Turbine External check valve opening only when the pressure difference from inlet to outlet is above a defined pressure difference and closing in the opposite case burst disk initially closed and opening when the pressure difference from inlet to outlet reaches a defined pressure difference Always opened afterwards volumetric pump providin
27. elow counter currentHX input Simulation of a counter current heat exchanger formed by two pipes thermally linked Run this file to generate a binary storage for later post processing with counter currentHX post Begin Simulation title counter currentHX Volumes 4 Junctions 2 Links 1 StartTime 0 0 EndTime 10 0 OutputStep 0 1 TimeMethod EulerBackward O CryoSoft 2013 Chapter 3 Case Studies 19 MinimumStep 1 0e 3 MaximumStep 1 0 StepEstimate smooth ErrorEstimate change ErrorControl on Tolerance 1 0e 6 StorageFile counter currentHX store LogFile counter currentHX log End The manifold volumes are defined as in the case of the parallel flow heat exchanger Note how later in the definition of the second pipe the input and output volumes are inverted with respect to the case of the parallel flow heat exchanger Begin Volume 1 inlet volume node V 1 0e6 P 5e5 T 300 0 End Begin Volume 2 outlet volume node V 1 0e6 P 4 95e5 T 300 0 End Begin Volume 3 inlet volume node V 1 0e6 P 5e5 T 320 0 End Begin Volume 4 outlet volume node V 1 0e6 P 4 95e5 T 300 0 End Begin Junction 1 type Cpipe connection 1 2 L 10 0 A 3 14e 4 Dh 1 0e 2 N 300 WP 3 14e 2 End The second pipe connects volume 4 location x 0 in the pipe to 3 location x L in the pipe As the pressure in volume 4 is lower than in volume 3 this results in backflow in this pipe i e in the direction of neg
28. eved as described above the resulting equations form a system of ordinary differential equations in time The solution of this system is performed in FLOWER using an implicit time stepping algorithm which can be selected by the user to be either of first or second order accuracy FLOWER advances the time integration by automatically adapting the time step based on a tolerance provided by the user various error control criteria that can be selected from input and maximum and minimum time step bounds The adaptive stepping automatically limits the change of the system variables pressure temperature and velocity and thus achieves accurate and stable results in the presence of the non linearity inherent to fluid flow Post processing The results produced by FLOWER are integrally stored and can be analyzed to produce plots and reports by the post processor FLOWERPOST FLOWERPOST responds to a user friendly command language and allows selection of results in time or space plot and print out of results vs time or space parametric plot of results at given time or space coordinate See the case studies in Chapter 3 for examples of post processing sessions and Chapter 5 for the details on the syntax of the command language User Flexibility and Further Extensions FLOWER has several features that allow customizing its modeling capability beyond the allowable parameterization of the thermal hydraulic electric configuration that can be achieved using
29. g a massflow either constant or user s defined compressor providing a massflow depending on the pressure difference from inlet to outlet turbine resulting in a localised pressure loss and isentropic state change from inlet to outlet the junction parameters are obtained from one of the other CryoSoft simulators through explicit coupling at each time step This coupling requires execution under the SuperMagnet environment and leads to an error in case it is used in stand alone mode See the SuperMagnet manual for more details 8 m Wetted perimeter only used for junction type Cpipe in case of heat exchange with other pipes or volumes The wetted perimeter is used in this case to compute the contribution of the thermal resistance from the flow to the pipe wall CryoSoft 2013 Chapter4 Input Reference 33 gt g gt a 3 O v z A S a a O fot hf 2 A Q n Sj g P A A z o o gt p 5 2 D U N fat a g ad a 3 4 re v ap n 7 ba U a T Q 3 p 3 n q v 5 amp x 5 6 a a O fl 8 oO L vA s s vA vA J J J A s 4 s lt s 4 s v vA Dh s v WP vA IN 4 fModel FrictionFactor J J icsiModel csi J J J J IhModel Dp v 4 Heating Iq J Tauq 4 PressureHead DpO 4 Massflow mO J v Table 1 Set of data needed for the definition of each type of junction A v entry
30. he binary stored results from FLOWER The default file name for printed output is f lower store Opening and reading of the CryoSoft 2013 44 binary storage file is automatic after parsing the first command Therefore this command if present must be the first in the post processing command file Supports and targets All plotting and print out actions of the post processor FLOWERPOST need the selection of a target to be plotted printed and the relative support A target is a variables or an auxiliary quantity computed in the simulation e g temperature A support is the component on which the quantity is defined e g volume component number 2 Target and support must be selected from a valid combination e g temperature of volume component number 2 In the following table we report the keys for the valid combinations of targets and supports Any invalid selection or combination of target and support results in a syntax error during parsing Support Target Units Meaning Volume Density kg m Fluid density in the volume Enthalpy J kg Fluid enthalpy in the volume QExternal W External heating power in the volume Pressure Pa Fluid pressure in the volume Temperature K Fluid temperature in the volume Junction Density kg m Fluid density in the junction Enthalpy J kg Fluid enthalpy in the junction Friction Friction factor of the flow in the junction HTC W m K heat transfer coefficient of the flow in the j
31. ime Tend 0 98987 Time 4 998E 03 Step 4 852E 05 Time Tend 0 99957 until the end of the simulation When the end time of the simulation is reached FLOWER prints a message reporting the total CPU time used in the run Total Cpu s 244 059998 Each run of FLOWER produces a binary storage file containing all results stored at user s specified times The user can control the name of this file the default file name is flower store a log file containing a report on the case run run statistics and error messages The user can control the name of this file the default file name is flower log Restart After a successful completion of a run it is possible to restart the simulation at the last time stored in the binary storage file and proceed with the time integration A restart procedure is triggered if the input file read by FLOWER contains the Restart command see Chapter 3 and 4 for details Assuming that this is the case for the input file file restart a restart in our example is obtained launching again FLOWER CryoSoft bin flower Enter input file name file restart in which case FLOWER reads the binary storage file and starts the simulation at the last time stored Time 5 000E 03 Step 1 000E 05 Time Tend 0 00000 CryoSoft 2013 Chapter2 Installing and Running FLOWER 11 Until the final time specified in the input file file restart is reached Note You can use an arbitrary sequence of restarts
32. is a string whose Value is read as a text delimited by apexes if the text contains a blank not recommended Integer VariableName is an integer whose Value is read according to FORTAN READ conventions Real VariableName is a real whose Value is read according to FORTAN READ conventions floating point or scientific notation The variables defined in the variables block are accessed from the External Routines and elsewhere in subroutines and functions linked at run time through calls to the function getXVariable VariableName Value where x stands for the variable type i e C I or R as described in 7 CryoSoft 2013 Chapter4 Input Reference 39 Standard definitions FLOWER uses standard definitions for the friction factor and heat transfer coefficient in pipes loss coefficient in valves and for the relation of massflow to pressure head in compressors These are taken as default in case the user does not select a specific option in input The definitions are given in the following sections Friction factor The friction factor is defined such that the pressure drop is given by 2 dp vo bc eg hy PD where fis given as a function of the Reynolds number Re Different pre programmed available correlations can be chosen in input among standard definitions reported in 5 The default definition is based on the friction factor as defined by the correlation of Blasius limited at low Reynolds number by the laminar
33. led if Heating user Parameter Type Units Meaning iv I Volume number time R s Simulation time p R Pa Volume pressure T R K Volume temperature qo R W Reference power as from input tau0 R s Reference heating time as from input Pipe Heating real function userPHeating ij time X T q0 rtau0 Returns the heating power deposition W m in a pipe Called if Heating user for a junction of type Cpipe The calculation is performed at all nodes of the junction identified by their nodal coordinate Parameter Type Units Meaning ij I Junction number time R s Simulation time x R m Node coordinate from inlet T R K Temperature at the node qo R W m Reference power as from input tau0 R s Reference heating time as from input Pipe Heat Transfer Coefficient real function userHTC ij time x T p D Dh Reynol HTC Returns the heat exchange W m K ina pipe Called if tc user for a junction of type Cpipe The calculation is performed at all nodes of the junction identified by their nodal coordinate Parameter Type Units Meaning ij I Junction number time R s Simulation time x R m Node coordinate from inlet T R K Temperature in the node p R Pa Pressure in the node D R Kg m Density in the node Dh R m Hydraulic diameter of the junction Reynol R Reynolds number of the flow at the node HTC R W m K reference heat transfer coefficient as from input
34. ler backward or full implicit or 6 1 method 1 order accurate default Galerkin Galerkin or 6 2 3 method 1 order accurate CrankNicolson Crank Nicolson or trapezoidal or 6 1 2 method 2 order accurate Tolerance R Relative error to be achieved at each time step during time integration used to control the time step Title C Problem title Volumes I Total number of volumes CryoSoft 2013 38 Variables The variables block is used to define user variables with given name and type stored internally and shared among routines and procedures The value of these user defined variables is accessible through a simple calling protocol in FORTRAN which greatly simplifies the preparation and parameterization of External Routines Variables can be seen as an extension of the standard input parameters i e a facility for easy customization Variables are defined with the following syntax VariableType VariableName Value where VariableType is one of the types defined in the table below VariableName is the name assigned to the variable and used later to retrieve its value and Value is the value of the appropriate type assigned to the variable Note We report below a short form of the variables syntax For further reference and for explanations on how to access variables from customized External Routines consult the Variables manual 7 VariableType Meaning Character VariableName
35. locity along the two pipes of the parallel flow heat exchanger at different times showing steady state conditions reached after 1 s from the beginning of the simulation CryoSoft 2013 18 Counter flow heat exchanger Physical definition of the problem In this test case we consider a counter flow heat exchanger with the same characteristics taken for the parallel flow heat exchanger described in the previosu section The topology for this case is shown in Fig 4 Note that this is nearly identical to Fig 2 apart for the different pressure and temperature in the two volumes that model the manifolds for the second pipe Having chosen a higher pressure at outlet results in backwards flow in this pipe The value of the thermal resistance is also modified to a lower value of 0 05 K W m 300 K L 10 m 300 K 5 bar A 3 14 cm 4 95 bar Dh 1 cm 2 2 2 TR 0 05 K W m YY VY L 10 m A 3 14 cm 300 K Dh 1cm 320 K 4 95 bar 5 bar Figure 4 Schematic view of the model for the analysis of the temperature in the two pipes forming a counter current heat exchanger The characteristics are identical to those reported in Fig 2 apart for the values of the pressures in the manifolds of the second pipe Input file for the run The input for this run requires the definition of the same number of components as for the parallel flow heat exchanger 4 volumes 2 pipes and 1 thermal link The step by step definition of the input file is shown b
36. loped is Macintosh running MacOS X 10 8 5 and higher under XQuartz 2 7 4 gcc 4 8 1 with gfortran The code has been installed and tested on the following platforms e IBM RISC workstations running the AIX OS Sun microsystem workstations running the Solaris OS e DEC alpha workstations running OSF1 OS e HP workstations running HP UX OS e INTEL PC s running RedHat Linux OS e Linux boxes running on Scientific Linux SLC dialect Although UNIX obeys strict standards the architecture of the operating and file system may vary from vendor to vendor It is therefore possible that porting may require minor adaption of code and libraries Contact us for advice In the following sections we assume here that you are running under a UNIX or UNIX like operating system and that you are familiar with UNIX commands directory and file handling Contact your system administrator for matters regarding UNIX commands and file system Although versions of FLOWER and FLOWERPOST have been ported to PC s running the Windows OS at the time when this manual is written this is not a platform directly supported and part of the instructions provided below i e how to run and post process a case may not be directly applicable Installation FLOWER is one of the CryoSoft family of programs You will have therefore received the CryoSoft package containing FLOWER either as a tar ball or in pre installed form Verify in the CryoSoft installatio
37. low the two pipes have a length of 10 m and an internal diameter of 1 cm The friction factor and heat transfer coefficient for the flow are obtained from the standard correlations 300 K L 10 m 300 K 5 bar A 3 14 cm 4 95 bar Dh 1cm 2 2 gt TR 0 1 K W m YY VY L 10 m A 3 14 cm 320 K Dh 1cm 300 K 5 bar 4 95 bar Figure 2 Schematic view of the model for the analysis of the temperature in the two pipes forming a parallel current heat exchanger The thermal resistance indicated with TR represents only the contribution of the pipe walls and possibly any intermediate thermal barrier but does not include the heat transfer from the flow to the pipe wall through the thermal boundary layer This last is computed automatically for the two flows Input file for the start up run The model for this case requires the definition of four volumes the manifolds the two pipes connecting them and the thermal link between the pipes The step by step definition of the input file for FLOWER start up run is shown below CryoSoft 2013 co currentHX input Simulation of a parallel current heat exchanger formed by two pipes thermally linked Run this file to generate a binary storage for later post processing with co currentHX post Begin Simulation title co currentHX The total number of volumes junctions and links in the model defined subsequently must be given before reading the definition of each componen
38. n manual 4 the procedure to be followed for the proper installation of the complete package The executable codes flower and flowerpost are in the directory CryoSoft 2013 10 CryoSoft bin You will find the example inputs and post processing command files in the directory CryoSoft xample flower code_x x the symbol stands for your home directory x x is the version you received How to run FLOWER Start up To run FLOWER you will need to launch the executable code In the standard installation on a UNIX system described above FLOWER is launched typing the command CryoSoft bin flower Once launched the program prompts the user for the input file name FLOWER reads the problem definition from an ASCII file whose structure and content are described in detail in Chapter 4 of this manual Examples of input files are given in Chapter 3 At this time you will enter the name of a file containing the input for the case to be run e g file input Enter input file name file input FLOWER then parses the input file performs checks on consistency configures the case and starts the simulation A simulation starts from an initial condition at the starting time and advances in time using the time step selected At each time step FLOWER emits a message with the real time reached in the simulation in s the time step taken in s and the ratio of real time to the total time to be simulated Time 4 949E 03 Step 3 235E 05 T
39. n the code If you are using External Routines verify their consistency with the calling protocol In case you are not using External Routines report internal consistency errors to us CryoSoft 2013 50 CHAPTER 8 References 1 2 3 4 5 6 7 8 Bottura L Quench Propagation through Manifolds in Forced Flow Cooled Coils IEEE Trans Appl Sup 3 1 606 609 1993 Bottura L Rosso C Hydraulic Network Simulator Model CryoSoft Internal Note CRYO 97 4 1997 Bottura L Rosso C Flower a Model for the Analysis of Hydraulic Networks and Processes Paper presented at Workshop on Computational of Thermo Hydraulic Transients in Superconducting Magnets CHATS 2002 Karlsruhe September 2002 Cryogenics 43 3 5 215 223 2003 CryoSoft Installation Manual Version 8 0 2013 Bottura L Friction Factor Correlations CryoSoft Internal Note CRY0 98 009 1998 Bottura L Heat Transfer Correlations CryoSoft Internal Note CRY0 98 010 1998 CryoSoft Variables Manual Version 1 0 2013 CryoSoft SuperMagnet Manual Version 2 1 2013 CryoSoft 2013
40. name can be changed only before the first plot is generated The command is ignored if a PostScript output has already been generated on another file or on the default file Print target target target support support SUPPOTt m Generate a table of n x m columns of the target s in the support s for every time or space coordinate selected see the Select command Note that several targets and supports can be printed simultaneously Example print temperature pressure volume 1 volume 2 Query query option List to standard output the input setting of query option this can be one of the BlockName identifiers as for the input simulation file Volume Junction Links Simulation or A11 to list the complete input set Reset EndTime Reset the end time for plots and listings to the last simulation time stored in the binary storage file Reset EndX Reset the end spatial coordinate for plots and listings to the default length of the support Reset StartTime Reset the start time for plots and listings to the first simulation time stored in the binary storage file Reset Startx CryoSoft 2013 Chapter5 Post processing Language Reference 43 Reset the start spatial coordinate for plots and listings to 0 Select Time t t gt vie ty Select from the binary storage file the results at times closest to the specified times The following Plot and Print commands will report the results as function of the spatial coo
41. number of junctions in the hydraulic network MaxLinks maximum number of thermal links in the hydraulic network MaxJNodes maximum total number of nodes in compressible flow pipe junctions The additional parameter SystemMatrixSize is automatically set to accommodate the sparse system matrix in the equation solver and should not need adjustments Contact us should the solver require more workspace memory The version of the code you received can be modified by adjusting these parameters as desired The code then needs to be compiled and link edited as explained in the installation manual you received 4 Warning Modification of dimensioning parameters affects memory allocation Improper programming of parameters can therefore corrupt operation and lead to evident or concealed malfunctions and generate manifest or hidden errors in the computed results IN NO EVENT WILL CRYOSOFT BE LIABLE FOR DIRECT INDIRECT SPECIAL INCIDENTAL OR CONSEQUENTIAL DAMAGES RESULTING FROM ANY AUTHORISED OR UNAUTHORISED USE OF THIS FEATURE even if advised of the possibility of such damages Internal consistency errors Internal consistency errors indicate corruption of the internal data structure of the program An internal consistency error cannot be generated using the standard program and reading data from input only However they can be detected in case that customized External Routines with improper data handling are used They diagnose a severe fault withi
42. onnection JV junction to volume connection vV volume to volume connection CryoSoft 2013 Chapter4 Input Reference 35 Simulation The simulation block describes the numerical parameters for time integration logging and storage of results Variable Type Units Meaning EndTime R s End time to be reached with the simulation ErrorControl C Switch for iterative error control during time integration Possible values none the time step is not iterated on ateach time step a check is performed to verify that the integration error is below the specified Tolerance If this is not the case the time step is changed and the integration is tried again iterating until the tolerance error is reached default ErrorControl on requires that an ErrorEstimate method is provided change or halving and that a StepEstimate is allowed smooth or power The iteration can significantly increase CPU time ErrorEstimate C Flag for the method used to estimate the time integration error control during a time step Possible values none no error estimate is provided change the error is estimated based on the change of the system solution during a time step default halving the error is estimated comparing the result obtained with a time step with the result obtained using two subsequent time steps of halved magnitude This method can significantly increase CPU time Fluid C Name of the fluid flowing in the network mo
43. ot velocity junction 4 plot massflow junction 4 select x 0 0 5 10 0 plot temperature junction 1 plot temperature junction 2 plot pressure junction 1 plot pressure junction plot velocity junction plot velocity junction plot massflow junction plot massflow junction NENEN stop CryoSoft 2013 26 Results The post processor FLOWERPOST with the commands described above in the file Loop regulated post generated the PostScript output loop regulated ps The plots below are contained in the first page in the PostScript output This page shows temperature and pressure of the volumes in the network where the temperature increases during the first 100 s heating time and sharply drops as soon as the heating stops The pressure rises from the initial value of 5 bar to cap at 6 bar the regulation value until the heating stops and the pressure drops rapidly below the initial value of 5 bar because of the expulsion to the regulation volume that took place during the transient The massflow in the branches is affected by the regulation actions i e the opening and closing of the check valve junction 7 not shown This being abrupt the massflow in the other junctions also experiences sharp variations volume 1 volume 1 volume 2 volume 2 volume 3 _ volume 3 FLOWER 4 4 7 12 2013 Vogne 54 Heated helium loop with T and UNG dt ion ar oe volume cop wita Sanyo lume SSS
44. overrides previous values and is not checked at read in time the blocks in the file are read sequentially and are checked at read in time This means that if Volumes Junctions links are requested then the Volumes and Junctions blocks must be assigned before the Links block The same BlockName can appear more than once in a file Parsing of the input file is finished as soon as an end of file is found At this point the execution control is passed to the main program that executes checks on data consistency configures the run and launches the simulation For sample input files see Chapter 3 Input variables reference The following table contains in alphabetical order the keywords defining the input variables their physical dimensions and meanings for each block type Predefined possible values are reported in Courier The default value is indicated in the table and underlined Note In the tables below we use the following convention for the type of variables C character a string delimited by blanks tabs or apices R real a number in floating point or engineering notation I integer an integer number Typing must be respect in the input file to avoid errors or mis interpretation by the parser Volume The Volume block defines a fluid volume with uniform pressure and temperature and zero flow It defines the volume size initial conditions of pressure and temperature and possibly any external heating source The volume num
45. p CryoSoft 2013 Chapter 3 Case Studies 17 e PostScript file output co currentHX ps 1s generated running the post Results The PostScript file outp isg d running the p processor FLOWERPOST with the commands described above in the file co currentHX post Note You will need a PostScript viewer to look at the plots in the PostScript file The standard viewer usually installed on UNIX systems is gs Try to launch the viewer with the command gs co currentHX ps The plots below show the first page in the PostScript output co currentHX ps As requested in the commands file the three plots are the temperature pressure and velocity distributions in the junctions 1 and 2 at selected times FLOWER 4 4 7 12 2013 9 58 45 co currentHX junction 1 _ junction 1 _ junction 1 SSS junction 2 SS ee junction 2 SSS 5 junction 2 a SLU BLEU nn TTT a oo Bp opt 4 o A 1 00E 01 s 7 A 1 00E 01 s J J 1 00E 01 s C Bx 1 00E 00 s 7 C B N1 00E 00 s J B 00E 00 s rs pes R002401 s E a p C 00E 01 s 3 72 C A O0RSO1 A C Sow J R als 4 za A v E aca J gt RE J Ba L a s I oF J Bet io sg E J gt amt 3 C J 8 H L a J vo o a E 4 a F o E J es E F H of 4 vo ae E fi ee J gt rig E SE J C vt J PA Al D TE R TAN B E TE A ar Errastiri ieg hia Ay iE T EE T a E E E E r A ET no 5 10 0 5 10 0 5 10 X m X m X m Page 1 Figure 3 Temperature pressure and flow ve
46. posite direction in the two pipes resulting in approximately equal but opposite flow speed As in the case of the parallel flow heat exchanger nearly steady state conditions are reached within 1 s of the start of the evolution The file counter currentHX out contains the output requested We report here only an abridged version of the full file The file can be read e g with a spread sheet program to produce more elaborate plots and further analysis of the results counter currentHxX out The following is the output of the results In our case the temperature at times 0 1 1 and 10 sec in the junctions I and 2 as a function of x for all coordinates stored in the binary storage file FLOWER Version 4 4 file created at 7 12 2013 10 08 29 Storage file counter currentHX store lines omitted junction 1 junction 2 X Temperature Temperature Temperature Temperature Temperature Temperature m K K K K K K 1 00E 01 s 1 00E 00 s 1 00E 01 s 1 00E 01 s 1 00E 00 s 1 00E 01 s 0 0000E 00 3 0000E 02 3 0000E 02 3 0000E 02 3 0224E 02 3 0631E 02 3 0684E 02 3 3333E 02 3 0001E 02 3 0004E 02 3 0004E 02 3 0227E 02 3 0633E 02 3 0686E 02 lines omitted 9 9667E 00 3 0466E 02 3 1245E 02 3 1298E 02 3 1990E 02 3 1995E 02 3 1995E 02 1 0000E 01 3 0467E 02 3 1247E 02 3 1300E 02 3 2000E 02 3 2000E 02 3 2000E 02 lines omitted CryoSoft 2013 22 Regulated circulation loop Physical definition of the problem In
47. rdinate at the n requested times The selection is overridden by a following Select command Select X X X2 si Xn Select from the binary storage file the results at the positions specified Interpolation is performed if the specified positions fall between nodes The following Plot and Print commands will report the results as function of the time at the n requested positions The selection is overridden by a following Select command Set Color on off Switch among color coding and dashed line coding B W for curves plotted for different supports in the same plot frame default is of f i e dashed line coding Set EndTime t Set the end time for plots and listings default is the last time stored in the binary storage file Set EndX x Set the end spatial coordinate for plots and listings default is the simulated Length Set PlotsPerPage n Set the number of plots per page The number n must be an integer equal to 1 2 3 4 or 6 6 being the default Changing the number of plots per page will automatically generate the plots to a new page Set StartTime t Set the start time for plots and listings default is the first time stored in the binary storage file Set StartX x Set the start spatial coordinate for plots and listings default is the simulated 0 Stop Stop execution and close the session An end of file during parsing of the command file results in the same effect StorageFile name Set the name of the file containing t
48. s Details on the model and a description of the equations solved are given elsewhere 2 3 inlet outlet manifold manifold parallel pipes control valve heat exchanger relief valve storage Figure 1 Schematic view of an hydraulic network as can be modeled and solved by the network solver FLOWER The nomenclature is indicated for clarity In this example two parallel pipes are connected through manifolds to a controlled pump and heat exchanger Any pressure excess in the loop is accommodated discharging through the relief valve in the storage CryoSoft 2013 Model Solution The equation for the network of hydraulic components in FLOWER are detailed in 2 3 The solution is based on the use of finite elements in space and a time stepping algorithm The volumes in the network are the nodes in the mesh where mass and energy balances are written in discrete form note that velocity is assumed to be zero in the volumes and hence the momentum balance is not used Most hydraulic junctions steady state flow pipes valves pumps and compressors turbines are discretized as a single finite element with mass momentum and energy balances written at the inlet and outlet nodes which correspond to volumes connected by the junction in the network Compressible flow pipes are treated similarly except for the fact that they have an arbitrary number of internal nodes Once the discretization in space is achi
49. sistance Length of the junction In the case of a volumetric pump junction type Pump this variable is the constant massflow provided by the pump In the case of a compressor junction type Compressor this is the maximum massflow that is provided by the compressor when the pressure head is zero Definition of the characteristics of the relation of massflow and pressure head in the case of pumps only CryoSoft 2013 Chapter4 Input Reference 31 used for junction type Pump or Compressor Possible values standard the standard relation is used to define the characteristics of the pump For a junction of type pump the massflow is constant equal to m0 For a junction of type compressor the massflow depends quadratically on the pressure head see the end of this chapter for more details default user the characteristics of the pump or compressor is defined through a user routine Note The feature of a user defined massflow characteristics is not yet active in this version of FLOWER Unpredictable results will be generated if the input file contains this keyword selection N I Number of elements used for meshing only for junction type CPipe PressureHead C Definition of the characteristics of the relation of massflow and pressure head in the case of a compressor i e only used for junction type Compressor Possible values standard the standard relation is used to define the characteristics of th
50. t Volumes 4 Junctions 2 Links 1 The time integration starts at StartTime and ends at EndTime with binary output of the results every OuputStep StartTime 0 0 EndTime 25 0 OutputSstep 0 1 Definition of the time stepping algorithm minimum and maximum steps error control strategy for the time integration and tolerance to be achieved TimeMethod EulerBackward MinimumStep 1 0e 6 MaximumStep 1 0 StepEstimate smooth ErrorEstimate change ErrorControl on Tolerance 1 0e 6 Log output is directed to the file co currentHX log while results are stored in the file co currentHX store for later restart and reporting StorageFile co currentHX store LogFile co currentHxX log End Here is the definition of the inlet and outlet volumes for the first pipe junction I below Note the large volume assumed to make the manifold equivalent to an infinite reservoir at constant pressure and temperature Begin Volume 1 inlet volume node V 1 0e6 P 5e5 T 300 0 End Begin Volume 2 outlet volume node V 1 0e6 P 4 95e5 T 300 0 End Inlet and outlet volumes for the second pipe junction 2 below The inlet manifold for this pipe has an higher temperature than for CryoSoft 2013 Chapter 3 Case Studies 15 the first pipe which will result in heat exchange between the two flows Begin Volume 3 inlet volume node V 1 0e6 P 5e5 T 320 0 End Begin Volume 4 outlet volume node V 1 0e6 P 4 95e5 T 300 0
51. the junction This variable represents the head loss factor and must be defined in the case of valve junctions i e type ControlValve CheckValve or Burstdisk or fora Turbine type see 3 Used if csiModel is constant This variable defines the calculation of the head loss factor in a valve or turbine and is needed in the case of valve junctions i e type Controlvalve CheckValve Burstdisk or for junctions of type Turbine Possible values constant the head loss factor is constant as given by the variable csi user user defined through the function userCsi see Chapter 6 Hydraulic diameter only used for junction type SSPipe or CPipe Threshold pressure difference determining opening closing of a check valve or breaking of a burst disk Only used for junction type CheckValve or BurstDisk Maximum pressure head provided by a compressor under zero massflow See the end of this chapter for more details Only used for junction type Compressor This variable defines the correlation used to compute the friction factor and is used in the case of junctions of type SSPipe and Cpipe see the end of this chapter for more details Possible values user user defined through the function UserFrictionFactor see Chapter 6 CryoSoft 2013 30 FrictionFactor Heating HTC hModel m0 Massflow constant constant in time and space equal to FrictionFactor as defined in input Blasius Blasius correla
52. this test case we consider a helium loop with a circulator constant mass flow pump flowing helium in parallel in two pipes of which one is heated for a time of 100 s The two pipes are in thermal contact with each other and exchange heat as the temperature of one increases The inlet temperature of the parallel pipes is regulated thanks to a heat exchanger model formed by a compressible flow pipe thermally linked to a large volume of helium that provides the heat sink The pressure in the loop tends to increase because of the effect of the heating and the maximum pressure is kept below a set value by a relief valves that opens in a large buffer volume that provides an infinite exhaust L 10 m A A 3 14 mm ah orm gt 3 W 3 14 mm 3 TS PFS SPST SPT FF Cc 4 5K 5 bar control valve 45K 5 bar 1m relief valve Dp 1 bar Figure 6 Schematic of the loop formed by a two parallel pipes of which one is heated The two pipes are thermally linked The helium flow is provided by a volumetric pump and is cooled by a heat exchanger realized by a pipe thermally linked with a large helium volume A check valve opening when the pressure difference between the two ends is larger than 1 bar provides pressure regulation to the loop Values of initial pressure and temperature and basic characteristics of the components are given in the schematic Input file for the run The input for this run requires the definition of 7 volumes 7 junc
53. tion Katheder Katheder correlation for CICC s Nikuradse Nikuradse von Karman correlation Smooth smooth tube correlation Westinghouse Westinghouse correlation for CICC s Friction factor to be used for frictional pressure drop calculation in pipe junctions i e of of type SSPipe and Cpipe Used if Model is constant Heating type it can be different from none only for a compressible pipe junction of type CPipe Possible values none no heating default window the heating is defined as constant equal to q in an interval 0 lt t lt Tauq and zero outside this interval See the end of this chapter for more details user user defined through the function userPHeating see Chapter 6 R W m K Heat transfer coefficient to be used for heat transfer R m Kg s calculation in pipe junctions i e of of type SSPipe and Cpipe Used if hModel is constant This variable defines the correlation used to compute the heat transfer coefficient and is used in the case of junctions of type SSPipe and Cpipe see the end of this chapter for more details Possible values user user defined through the function UserHTC see Chapter 6 constant constant in time and space BLQ Boundary layer filling with step in wall heat flux BLT Boundary layer filling with step in wall temperature DB Dittus B lter correlation DBG Dittus B lter Giarratano correlation for supercritical helium Kapitza Kapitza thermal re
54. tions and 2 thermal links In this case which remains relatively simple the control valve has constant opening and the check valve that controls pressure is either fully opened or closed Better control and more physical results could be obtained by defining valves with gradual opening and closing which can be done in FLOWER using the External Routines mechanism The step by step definition of the input file is reported below with interspersed comments CryoSoft 2013 Chapter 3 Case Studies 23 loop regulated input A more complex loop formed by a two parallel pipes of which one is heated The two pipes are thermally linked The helium flow is provided by a volumetric pump The flow is cooled by a heat exchanger realised by a pipe thermally linked with a large helium volume A check valve opening when the pressure difference between the two ends is larger than 1 bar provides pressure regulation to the loop Run this test file first then post process using the loop regulated post file F Begin Simulation Title Heated helium loop with T and p regulation Volumes 7 Junctions 7 Links 2 StartTime 0 0 EndTime 200 0 OutputStep 0 1 TimeMethod EulerBackward MinimumStep 1 0e 6 MaximumStep 1 0 StepEstimate smooth ErrorEstimate change ErrorControl on Tolerance 1 0e 3 StorageFile loop regulated store LogFile loop regulated log End Begin Volume 1 inlet manifold V 1 0e 6 P 5e5 T 4 5 En
55. to simulate different time spans with varying resolution and accuracy There is no limit to the number of restarts that can be executed for a single simulation How to run FLOWERPOST To produce any detailed result both in the form of printed tables or plotted curves in PostScript amp format it is necessary to run the FLOWER post processor FLOWERPOST FLOWERPOST is launched under UNIX with the command CryoSoft bin flowerpost FLOWERPOST prompts the user for the name of an ASCII file containing the series of commands that control the generation of the printouts and plots The structure and content of this file is described in detail in Chapter 5 of this manual Examples of command files are given in Chapter 3 At this time you will enter the name of the file containing the commands e g file post Enter command file name file post FLOWERPOST then parses echoes and interprets the commands from the command file The commands cause retrieval of the results of a run from the binary storage file generated by FLOWER by default from the file flower store As a result FLOWERPOST generates a file containing the formatted printouts of the results by default flowerpost out and a file containing the plots requested in PostScript format by default flowerpost ps Customization The method described earlier provides the standard manner to run a FLOWER simulation and post process the results FLOWER however as most other Cr
56. unction Massflow kg s Fluid massflow in the junction Pressure Pa Fluid pressure in the junction QExternal W m External heating power in the junction Temperature K Fluid temperature in the junction Velocity m s Fluid flow velocity in the junction CryoSoft 2013 Chapter 6 External Routines 45 CHAPTER 6 External Routines Warning External Routines give unlimited access to the data structure used by the main program Improper programming of External Routines can therefore corrupt operation and lead to evident or concealed malfunctions and generate manifest or hidden errors in the computed results IN NO EVENT WILL CRYOSOFT BE LIABLE FOR DIRECT INDIRECT SPECIAL INCIDENTAL OR CONSEQUENTIAL DAMAGES RESULTING FROM ANY AUTHORISED OR UNAUTHORISED USE OF THIS FEATURE even if advised of the possibility of such damages Linking external routines The External Routines for FLOWER are FORTRAN functions packaged in a series of files contained in the directory CryoSoft usr flower code x x where x x stands for the version you received which you will have received with the standard installation In order to customize the code you will need to write modified version of these files We strongly suggest to create your own directory tree within the above directory and to modify only copies of the External Routines in order to be able to safely retrieve the standard version at your wish Once the modified routines are ready
57. ut of range Verify the consistency of the input data in this case Runtime errors Runtime errors are detected either when the solver enters a physical or numerical instability or when the size of the problem exceeds the maximum allowed Physical instabilities can be CryoSoft 2013 Chapter 7 Troubleshooting and Errors 49 triggered by improper setting of physical conditions e g initial conditions or boundary conditions excessive transient conditions e g very large heating powers or pressure differences or because of incorrect values from fluid properties Verify input conditions in this case Numerical instabilities can be triggered y the use of very large time steps coarse mesh and algorithms with little to no damping In case of numerical instability attempt at reducing the maximum time step value of MaximumStep in input reducing the allowed integrator tolerance value of Tolerance in input or choosing a time integration method that is more robust choose EulerBackward as TimeMethod The maximum size of the network that can be solved is determined by the requested memory allocation in the FORTRAN include file CryoSoft src flower code_x x includes parameters inc where a number of parameters are set statically The main parameters affecting memory allocation are the following with the associated meaning Parameter Meaning MaxVolumes maximum number of volumes in the hydraulic network MaxJunctions maximum
58. volume 6 volume 6 volume 7 volume 7 SS PRTG T g N J o J E a B ig J RA m FH M q co El gt J a J amp El g E 3 sac Dakt B E i og BSE dg E q 5 4 Poe fof 3o z El aa E qf aE sp DE J A I a E H J a E a g E ea 0 100 0 3 Time s Time s 4 junction 3 5 junction 4 6 junction 1 _ junction 5 7 junction 2 junction 6 y Mm ae E a F A E J a E A 0 00E 00 a F 4 E m of 4 F D e a E ger 2 NI J Dap D a E J K E L f k BOF E E ad F 4 ad C a 2 of 1 3 3 mil k hy E aH d 8 E S 5 H J E Perret titre od 0 100 0 100 Time s Time s Time s Page 1 Figure 7 Temperature pressure density and enthalpy in the network volumes and massflow in selected junctions for the regulated loop test case CryoSoft 2013 Chapter4 Input Reference 27 CHAPTER 4 Input Reference Structure and syntax The input file is read by the input interpreter that parses and analyzes the syntax and the grammar of the various entries In general the file contains a series of blocks that are structured as follows Begin BlockName VariableName value s VariableName value s VariableName value s End where BlockName is a keyword indicating the block type and must be one of the following valid choices Volume define the general properties of
59. yoSoft codes gives the possibility to customize the physical models by using External Routines as described in Chapter 6 see later for details The user has the possibility to adapt and extend the physics contained in the standard solver at the additional complexity of writing FORTRAN routines that must obey to the language syntax and parameter call specification The customized External Routines need to be compiled and linked the program segments to generate the customized version of the code Template for the External Routines are given in the directory CryoSoft usr flower code_x x Compilation and link editing can be done using the standard installation script CSmake but we discourage users to modify the standard codes provided as this will replace the reference installation As a safer alternative we strongly recommend copying the External Routines templates in a work directory and generating in this location the customized version of the code by using an adapted compilation script or a makefile Consult the examples below and contact us for guidelines on how to set up one such customized structure CryoSoft 2013 12 CHAPTER 3 Case Studies As discussed in Chapter 2 FLOWER requires an input file with all definitions necessary to specify the assembly of components in the model structure the characteristics of each component the initial conditions and the solution controls We refer to this file as the input file The

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