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-   -   Concentric tube heat exchanger (Air-Water) (http://www.cfd-online.com/Forums/cfx/26451-concentric-tube-heat-exchanger-air-water.html)

Young October 1, 2008 03:50

Concentric tube heat exchanger (Air-Water)
 
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?


rohit October 2, 2008 07:50

Re: Concentric tube heat exchanger (Air-Water)
 
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

Young October 2, 2008 13:10

Re: Concentric tube heat exchanger (Air-Water)
 
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?


Glenn Horrocks October 2, 2008 19:11

Re: Concentric tube heat exchanger (Air-Water)
 
Hi,

Please post the CCL of the run at the top of the output file.

Glenn Horrocks

Young October 3, 2008 01:43

Re: Concentric tube heat exchanger (Air-Water)
 
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.


Glenn Horrocks October 7, 2008 00:17

Re: Concentric tube heat exchanger (Air-Water)
 
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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