Altair Employee
What you are plotting is the surface_film_coefficient, that is not really temperature dependent.
Please check following for three types of HTC calculations. You might want to use temperature based one.
Getting a high error in HTC for coolant jacket compared with ANSYS. Please check the file attached
sandeep123
Altair Community Member
I am trying to estimate the heat transfer coefficient for coolant jacket. Please verify the process followed. You may check the attached file for more details.
I am getting a different value compared with ANSYS CFD with a relative error>100%. Seek your observations on this matter.
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Answers
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What you are plotting is the surface_film_coefficient, that is not really temperature dependent.
Please check following for three types of HTC calculations. You might want to use temperature based one.
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Some old discssion on the same topic
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Try using the temperature based HTC.
You will need to create a formula like shown in the screenshot.
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The methods are not clearly explained in the notes. The equations are also not clear in the next response. Could you please elaborate? Is HTC = (heat flux)/(Tfluid average - Twall average))?In that case i am getting even higher HTCs
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q = h * A * (T - Tref)
where h is the heat transfer coefficient. This would then become
h = q / ( A * (T - Tref) )
q is the local heat flux, A is the local/nodal area, T is the local temperature, and Tref is the local reference temperature. This local reference temperature is as explained above, make sure the definitions are consistent.
In current release versions you can set the method used for HTC in the TURBULENCE_MODEL_PARAMETERS command. Look for htc_method on this page:Then you can plot htc directly based on that definition. You may need to manually add that command to the input file before running, like:
TURBULENCE_MODEL_PARAMTERS {
htc_method = user_ref_temperature
user_ref_temperature = 300.0
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The boundary condition for my problem is constant heat flux.
- Reading from the above document, i am unable to understand this "user reference temp". Could you please in your own words? (In my case, i cannot specify a particular temperature value. I tried to manually calculate also using this equation HTC = applied heat flux in W/m2 ,also the BC / (Tavg,wall - Tavg,fluid). Still there is a high error compared to actual results)
- The below portion in the document mentions that the surface film coefficient is also one of the ways to estimate HTC in Hypermesh CFD.
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When estimating area-averaged heat transfer coefficients, ensure that the reference temperature remains consistent in both cases.
For example, in your case:
HTC = Heat Flux / (Temperature at Fluid Surface - Reference Temperature)The reference temperature can be either the inlet temperature or the bulk volume-averaged temperature, but it must remain consistent when comparing HTC values across different software.
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How to check the reference temperature value in my problem?
HTC should be Heat flux/(Tavg,fluid-Tavg,wall) right?
What is the signifiance of reference temperature?Can you provide any definition?0 -
Nope, its actually Heat flux/(Tavg,wall - Tavg,fluid) since the heat is being transfered from the wall to fluid.
Tavg,wall is also called reference temperature.
With the given heat flux value (15625) and the average wall temperature (T_avg,wall) from AcuSolve results, you can manually estimate the heat transfer coefficient (HTC). To ensure consistency, use the same reference temperature (T_avg,fluid) as in ANSYS for the calculation.
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Which is reference temperature? Tavg,wall or Tavg,fluid?What is the value in my problem?
If i manually calculate it, HTC ~ 12000
But surface film coefficient ~ 9000
ANSYS HTC ~ 4000
ANSYS temperature range : 338 - 346
How to conclude?0 -
First task is to understand how Ansys computes HTC - if you want to compare to that. There is always some reference temperature used for HTC - and you need to find out what Ansys is using for that when reporting HTC. Then use the same approach in another software if comparing. It could be the temperature at a given distance from the wall, it could be an average temperature from somewhere, it could be a user-given value - any number of things. You need to determine what you're using for reference-temperature in Ansys. This might be useful:
https://innovationspace.ansys.com/courses/courses/topics-in-convective-heat-transfer-simulations/lessons/defining-heat-transfer-coefficient/
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