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October 1, 2008, 03:50 |
Concentric tube heat exchanger (Air-Water)
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#1 |
Guest
Posts: n/a
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Dear all,
I have tried to run a certain concentric pipe heat exchanger but now I'm frustrated. I made a model in design modeler of workbench as follows: 1) make inner circle and extrude it then the cylinder was freezed. 2) Make outter circle and extrude it then it is an encloser of the inner circle 3) Using "Form a part" to make two solids as one. Then I execute the mesh. There is no problem. In the CFX-Pre, I checked interface and inlet outlet condition. But It makes always the same error ; Writing crash recovery file | +--------------------------------------------------------------------+ ---------------------------------- Error in subroutine FNDVAR : Error finding variable DENSITY_FL1 GETVAR originally called by subroutine GET_MFLOIP_ZIF __________________________________________________ ___ I used the air at STC and Water at 25C, which have the density value (I have checked millon times) but CFX can not find the fluid density. Is it mesh problem? Is it geometry problem? I thought it is a simple heat exchanger problem but it's not. Who is the man to sucess running a concentric heat exchanger? Would you let me know how you do model and run the heat exchanger problem? |
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October 2, 2008, 07:50 |
Re: Concentric tube heat exchanger (Air-Water)
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#2 |
Guest
Posts: n/a
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Dear young,
are you properly defining the two domains in CFX pre..? did you checked whether you have selected cprrect fluid names from the fluid list for both the domians |
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October 2, 2008, 13:10 |
Re: Concentric tube heat exchanger (Air-Water)
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#3 |
Guest
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Thanks rohit for your concerns.
I selected the Air at STC in the fluid list of CFX-pre for air tube fluid. and Water (constant property liquid) in the fluid list. Am I worng? |
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October 2, 2008, 19:11 |
Re: Concentric tube heat exchanger (Air-Water)
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#4 |
Guest
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Hi,
Please post the CCL of the run at the top of the output file. Glenn Horrocks |
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October 3, 2008, 01:43 |
Re: Concentric tube heat exchanger (Air-Water)
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#5 |
Guest
Posts: n/a
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Hi,
Thank you for your concerns. I always appreciate your kind and valuable recommends in this web site. Here is my CCL for my simple but ugly heat exchanger. Hopefully, you can find what is wrong and what I should do. Thank you again. ++++++++++++++++++++++++++++++++++++++++++++++++++ +--------------------------------------------------------------------+ | | | CFX Command Language for Run | | | +--------------------------------------------------------------------+ LIBRARY: MATERIAL: Air at STP Material Description = Air at STP (0 C and 1 atm) Material Group = Air Data, Constant Property Gases Option = Pure Substance Thermodynamic State = Gas PROPERTIES: Option = General Material Thermal Expansivity = 0.00366 [K^-1] ABSORPTION COEFFICIENT: Absorption Coefficient = 0.01 [m^-1] Option = Value END DYNAMIC VISCOSITY: Dynamic Viscosity = 1.725E-05 [kg m^-1 s^-1] Option = Value END EQUATION OF STATE: Density = 1.284 [kg m^-3] Molar Mass = 28.96 [kg kmol^-1] Option = Value END REFERENCE STATE: Option = Specified Point Reference Pressure = 1 [atm] Reference Specific Enthalpy = 0. [J/kg] Reference Specific Entropy = 0. [J/kg/K] Reference Temperature = 0 [C] END REFRACTIVE INDEX: Option = Value Refractive Index = 1.0 [m m^-1] END SCATTERING COEFFICIENT: Option = Value Scattering Coefficient = 0.0 [m^-1] END SPECIFIC HEAT CAPACITY: Option = Value Specific Heat Capacity = 1.0038E+03 [J kg^-1 K^-1] Specific Heat Type = Constant Pressure END THERMAL CONDUCTIVITY: Option = Value Thermal Conductivity = 2.428E-02 [W m^-1 K^-1] END END END MATERIAL: Water Material Description = Water (liquid) Material Group = Water Data, Constant Property Liquids Option = Pure Substance Thermodynamic State = Liquid PROPERTIES: Option = General Material Thermal Expansivity = 2.57E-04 [K^-1] ABSORPTION COEFFICIENT: Absorption Coefficient = 1.0 [m^-1] Option = Value END DYNAMIC VISCOSITY: Dynamic Viscosity = 8.899E-4 [kg m^-1 s^-1] Option = Value END EQUATION OF STATE: Density = 997.0 [kg m^-3] Molar Mass = 18.02 [kg kmol^-1] Option = Value END REFERENCE STATE: Option = Specified Point Reference Pressure = 1 [atm] Reference Specific Enthalpy = 0.0 [J/kg] Reference Specific Entropy = 0.0 [J/kg/K] Reference Temperature = 25 [C] END REFRACTIVE INDEX: Option = Value Refractive Index = 1.0 [m m^-1] END SCATTERING COEFFICIENT: Option = Value Scattering Coefficient = 0.0 [m^-1] END SPECIFIC HEAT CAPACITY: Option = Value Specific Heat Capacity = 4181.7 [J kg^-1 K^-1] Specific Heat Type = Constant Pressure END THERMAL CONDUCTIVITY: Option = Value Thermal Conductivity = 0.6069 [W m^-1 K^-1] END END END END FLOW: SOLUTION UNITS: Angle Units = [rad] Length Units = [m] Mass Units = [kg] Solid Angle Units = [sr] Temperature Units = [K] Time Units = [s] END SIMULATION TYPE: Option = Steady State EXTERNAL SOLVER COUPLING: Option = None END END DOMAIN: Default Domain Modified Coord Frame = Coord 0 Domain Type = Fluid Fluids List = Air at STP Location = B114 BOUNDARY: Default Domain Modified Default Boundary Type = WALL Location = F115.114,F127.114,F142.114,F143.114 BOUNDARY CONDITIONS: HEAT TRANSFER: Option = Adiabatic END WALL INFLUENCE ON FLOW: Option = No Slip END WALL ROUGHNESS: Option = Smooth Wall END END END BOUNDARY: Default Fluid Fluid Interface Side 1 Boundary Type = INTERFACE Location = \ F117.114,F125.114,F119.114,F118.114,F116.114,F123. 114,F126.114,F121.1\ 14,F122.114,F120.114,F124.114 BOUNDARY CONDITIONS: HEAT TRANSFER: Option = Conservative Interface Flux END MASS AND MOMENTUM: Option = Conservative Interface Flux END TURBULENCE: Option = Conservative Interface Flux END END END BOUNDARY: ain Boundary Type = INLET Location = F128.114 BOUNDARY CONDITIONS: FLOW REGIME: Option = Subsonic END HEAT TRANSFER: Option = Static Temperature Static Temperature = -11.3 [C] END MASS AND MOMENTUM: Normal Speed = 1 [m s^-1] Option = Normal Speed END TURBULENCE: Option = Medium Intensity and Eddy Viscosity Ratio END END END BOUNDARY: aout Boundary Type = OUTLET Location = F129.114 BOUNDARY CONDITIONS: FLOW REGIME: Option = Subsonic END MASS AND MOMENTUM: Option = Average Static Pressure Relative Pressure = 0 [Pa] END PRESSURE AVERAGING: Option = Average Over Whole Outlet END END END DOMAIN MODELS: BUOYANCY MODEL: Option = Non Buoyant END DOMAIN MOTION: Option = Stationary END MESH DEFORMATION: Option = None END REFERENCE PRESSURE: Reference Pressure = 1 [atm] END END FLUID MODELS: COMBUSTION MODEL: Option = None END HEAT TRANSFER MODEL: Option = Thermal Energy END THERMAL RADIATION MODEL: Option = None END TURBULENCE MODEL: Option = k epsilon END TURBULENT WALL FUNCTIONS: Option = Scalable END END END DOMAIN: wat Coord Frame = Coord 0 Domain Type = Fluid Fluids List = Water Location = B130 BOUNDARY: Default Fluid Fluid Interface Side 2 Boundary Type = INTERFACE Location = \ F126.130,F119.130,F124.130,F125.130,F123.130,F122. 130,F117.130,F116.1\ 30,F120.130,F121.130,F118.130 BOUNDARY CONDITIONS: HEAT TRANSFER: Option = Conservative Interface Flux END MASS AND MOMENTUM: Option = Conservative Interface Flux END TURBULENCE: Option = Conservative Interface Flux END END END BOUNDARY: wat Default Boundary Type = WALL Location = \ F131.130,F132.130,F133.130,F134.130,F135.130,F136. 130,F137.130,F138.1\ 30,F139.130 BOUNDARY CONDITIONS: HEAT TRANSFER: Heat Flux in = -50 [W m^-2] Option = Heat Flux END WALL INFLUENCE ON FLOW: Option = No Slip END WALL ROUGHNESS: Option = Smooth Wall END END END BOUNDARY: watin Boundary Type = INLET Location = F140.130 BOUNDARY CONDITIONS: FLOW REGIME: Option = Subsonic END HEAT TRANSFER: Option = Static Temperature Static Temperature = 45 [C] END MASS AND MOMENTUM: Normal Speed = 0.3 [m s^-1] Option = Normal Speed END TURBULENCE: Option = Medium Intensity and Eddy Viscosity Ratio END END END BOUNDARY: wout Boundary Type = OUTLET Location = F141.130 BOUNDARY CONDITIONS: FLOW REGIME: Option = Subsonic END MASS AND MOMENTUM: Option = Average Static Pressure Relative Pressure = 0 [Pa] END PRESSURE AVERAGING: Option = Average Over Whole Outlet END END END DOMAIN MODELS: BUOYANCY MODEL: Option = Non Buoyant END DOMAIN MOTION: Option = Stationary END MESH DEFORMATION: Option = None END REFERENCE PRESSURE: Reference Pressure = 1 [atm] END END FLUID MODELS: COMBUSTION MODEL: Option = None END HEAT TRANSFER MODEL: Option = Thermal Energy END THERMAL RADIATION MODEL: Option = None END TURBULENCE MODEL: Option = k epsilon END TURBULENT WALL FUNCTIONS: Option = Scalable END END END DOMAIN INTERFACE: Default Fluid Fluid Interface Boundary List1 = Default Fluid Fluid Interface Side 1 Boundary List2 = Default Fluid Fluid Interface Side 2 Interface Type = Fluid Fluid INTERFACE MODELS: Option = General Connection FRAME CHANGE: Option = None END PITCH CHANGE: Option = None END END MESH CONNECTION: Option = GGI END END OUTPUT CONTROL: RESULTS: File Compression Level = Default Option = Standard END END SOLVER CONTROL: ADVECTION SCHEME: Option = High Resolution END CONVERGENCE CONTROL: Length Scale Option = Conservative Maximum Number of Iterations = 100 Timescale Control = Auto Timescale Timescale Factor = 1.0 END CONVERGENCE CRITERIA: Residual Target = 1.E-4 Residual Type = RMS END DYNAMIC MODEL CONTROL: Global Dynamic Model Control = On END END END COMMAND FILE: Version = 11.0 Results Version = 11.0 END EXECUTION CONTROL: INTERPOLATOR STEP CONTROL: Runtime Priority = Standard EXECUTABLE SELECTION: Double Precision = Off END MEMORY CONTROL: Memory Allocation Factor = 1.0 END END PARALLEL HOST LIBRARY: HOST DEFINITION: chae Installation Root = C:\Program Files\ANSYS Inc\v%v\CFX Host Architecture String = intel_xeon64.sse2_winnt5.1 END END PARTITIONER STEP CONTROL: Multidomain Option = Independent Partitioning Runtime Priority = Standard EXECUTABLE SELECTION: Use Large Problem Partitioner = Off END MEMORY CONTROL: Memory Allocation Factor = 1.0 END PARTITIONING TYPE: MeTiS Type = k-way Option = MeTiS Partition Size Rule = Automatic END END RUN DEFINITION: Definition File = F:/Thesis/prelim/test/002/minihs4.def Interpolate Initial Values = Off Run Mode = Full END SOLVER STEP CONTROL: Runtime Priority = Standard EXECUTABLE SELECTION: Double Precision = Off END LICENSE CONTROL: Preferred License = 35 Shared License Port = 2033 END MEMORY CONTROL: Memory Allocation Factor = 1.0 END PARALLEL ENVIRONMENT: Number of Processes = 1 Start Method = Serial END END END +--------------------------------------------------------------------+ | | | Solver | | | +--------------------------------------------------------------------+ +--------------------------------------------------------------------+ | | | ANSYS CFX Solver 11.0 | | | | Version 2007.01.15-19.20 Mon Jan 15 19:24:21 GMTST 2007 | | | | Executable Attributes | | | | single-int32-32bit-novc6-optimised-supfort-noprof-nospag-lcomp | | | | Copyright 1996-2007 ANSYS Europe Ltd. | +--------------------------------------------------------------------+ +--------------------------------------------------------------------+ | Job Information | +--------------------------------------------------------------------+ Run mode: serial run Host computer: CHAE Job started: Wed Sep 24 16:43:44 2008 +--------------------------------------------------------------------+ | Memory Allocated for Run (Actual usage may be less) | +--------------------------------------------------------------------+ Data Type Kwords Words/Node Words/Elem Kbytes Bytes/Node Real 217758.5 3146.16 955.78 850619.1 12584.65 Integer 60150.9 869.06 264.01 234964.4 3476.23 Character 2885.9 41.70 12.67 2818.2 41.70 Logical 65.0 0.94 0.29 253.9 3.76 Double 608.0 8.78 2.67 4750.0 70.27 +--------------------------------------------------------------------+ | ****** Notice ****** | | Wall Heat Transfer Coefficient written to the results file uses | | "Wall Adjacent Temperature" for the bulk temperature. If you want | | to override the bulk temperature then set the expert parameter | | "tbulk for htc = <value>" | +--------------------------------------------------------------------+ +--------------------------------------------------------------------+ | Mesh Statistics | +--------------------------------------------------------------------+ Domain Name : Default Domain Modified Total Number of Nodes = 29514 Total Number of Elements = 105046 Total Number of Tetrahedrons = 105046 Total Number of Faces = 39348 Minimum Orthogonality Angle [degrees] = 32.0 ok Maximum Aspect Ratio = 5.6 OK Maximum Mesh Expansion Factor = 17.0 ok Domain Name : wat Total Number of Nodes = 39700 Total Number of Elements = 122787 Total Number of Tetrahedrons = 122787 Total Number of Faces = 77494 Minimum Orthogonality Angle [degrees] = 34.6 ok Maximum Aspect Ratio = 13.4 OK Maximum Mesh Expansion Factor = 16.2 ok Global Statistics : Global Number of Nodes = 69214 Global Number of Elements = 227833 Total Number of Tetrahedrons = 227833 Global Number of Faces = 116842 Minimum Orthogonality Angle [degrees] = 32.0 ok Maximum Aspect Ratio = 13.4 OK Maximum Mesh Expansion Factor = 17.0 ok Domain Interface Name : Default Fluid Fluid Interface Non-overlap area fraction on side 1 = 0.00E+00 Non-overlap area fraction on side 2 = 0.00E+00 ---------------------------------- Error in subroutine FNDVAR : Error finding variable DENSITY_FL1 GETVAR originally called by subroutine GET_MFLOIP_ZIF +--------------------------------------------------------------------+ | Writing crash recovery file | +--------------------------------------------------------------------+ ---------------------------------- Error in subroutine FNDVAR : Error finding variable DENSITY_FL1 GETVAR originally called by subroutine GET_MFLOIP_ZIF +--------------------------------------------------------------------+ | An error has occurred in cfx5solve: | | | | The ANSYS CFX solver exited with return code 1. No results file | | has been created. | +--------------------------------------------------------------------+ End of solution stage. +--------------------------------------------------------------------+ | Warning! | | | | The ANSYS CFX Solver has written a crash recovery file. This file | | has been saved as F:\Thesis\prelim\test\002\minihs4_003.res.err | | and may be an aid to diagnosing the problem or restarting the run. | | More details should be available in the solver output section of | | the output file. Note that a lock file was left for the crash | | file when the solver exited, and so it is probably incomplete. | +--------------------------------------------------------------------+ +--------------------------------------------------------------------+ | The following user files have been saved in the directory | | F:\Thesis\prelim\test\002\minihs4_003: | | | | mon | +--------------------------------------------------------------------+ This run of the ANSYS CFX Solver has finished. |
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October 7, 2008, 00:17 |
Re: Concentric tube heat exchanger (Air-Water)
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#6 |
Guest
Posts: n/a
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Hi,
I can't pick the problem after a quick look. I would build the simulation up again, first one domain, then the other then other connected by an interface. Glenn Horrocks |
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