Hello Colleagues,
I am trying to simulate a helical heat exchanger, simulation is working fine however when I compare my SIM CFD results to theory/empirical solution I found it way off (so model not validated).
I am interested in a transient solution so I have tried to make the time step smaller and mesh size as well and still solution was still off. I rechecked my theoratical solution which was based on an example from a book there was nothing wrong and the only modification I made to simplify the CFD work is: I reduced the mass flow rate of both fluid in the shell and the helical tube and I played with the desired output and input temperautres to make heat exchanger compact so it wont take as much time to solve.
In autodesk CFD SIM: As i said it is a transient problem although I have tried steady state and solution was aslo different from both theory and the transient results. I advection 5 and solution controls where kept at default, turbulence default (K-epsilon), timestep size 0.05 and I also tried 0.1, mesh size: I had 1 million, 2 million, and 4 million elment cases.
I would appreciate any suggestions and or any resources you think could be helpful to solve my problem.
Note that I have
Thank you,
Ghaleb
What type of fluid do you have going through the HX?
How much error did you have with your steady state solution? I would not go to the transient setup until you have a good steady state solution.
-Royce
Hello Royce,
I am interested in the transient solution more, anyhow as per your suggestion let me share with you the steady state problem first and then if possible we go to transient.
I have defined two liquids, A and B see properties below. The coil is made of stainless steel. The cfz file for this case is too large to attach here.
My error for steady state is: % error of temperature of fluid A exiting coil = 41% and % error of temperature of fluid B exiting shell is around 76%.
CFD results: Steady: coil ( Tout: 70 degree C) and shell (Tout: 44 degree C).
Theory results: coil ( Tout: 120 degree C) and shell (Tout: 25 degree C).
In shell
Liquid B properties:
density: 935 kg/m^3
Mass flow rate: 0.138 kg/sec
Viscosity: 0.0016 Pa-s
Specific heat: 4183.995 J/Kg-k
Thermal Conductivity:0.4739225 W/m.k
Tin= 5 degree C
Tout = 25 degree C
and liquid A in coil:
density: 870 kg/m^3
Mass flow rate: 0.088 kg/sec
Viscosity: 0.000525 Pa-s
Specific heat: 4183.995 J/Kg-k
Thermal Conductivity:0.4812 W/m.k
Tin= 140 degree C
Tout = 120 degree C
I am going to try to run different simualtions using the given turbulent model in 2013 version. This version should be able to simulate this problem with a much lower error from what I am seeing now.
I would appreciate if you have any other suggestions that I could try as well.
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