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Negative heat flux and heat transfer coefficient at a surface !

    • Anadi_Mondal
      Subscriber

      Hello,

      I am simulating conjugate heat transfer in a nuclear fuel pin. Heat is generated in the fuel pellet and transferred to the liquid. I got the converged result. Now I want to calculate the heat transfer coefficient and heat flux at the cladding outside surface which is in contact with liquid. While I tried to get the surface heat transfer coefficient, I see the heat transfer coefficient was negative. I set the reference temperature of 566.25K where the inlet temperature is also 566.25K. The bulk temperature of the liquid increased to 612.25K at the outlet. 

      HTC is dependent on the reference value. So, what should be the reference for this reference temp? 

      What may be the reason for getting the negative value of  HTC and total heat flux even though the surface temperature is always greater than the bulk/inlet temperature?

      Is there any other way to get heat transfer and HTC? I am using a k-epsilon model with a wall function for turbulence modeling.

      Regards,

      Anadi

    • DrAmine
      Ansys Employee

      Reference Temperature is user input an you should know better about that than we do. If nothing mentioned in experiments, publications, correlations you compre with, I will use either saturation temprature or inflow temperature.

      Sign of HTC will depend on the temperature diffrence ( and hence on reference temprature) and the heat flux (inward/outwards).

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