heat transfer coefficient

James_Wang

Hi, anyone can give me idea, how can I calculate heat transfer coefficient.
My problem is a alu housing containing electrical  device, which generating heat.
The housing has complicated shape and ambient temparature is 60 C. Anyone can tell me, how can I use Ansys CFD to calculate heat transfer coefficient, which parameters do I need?

Many thanks!

courageddt

Hi, James

It seems that you encountered with a heat sink simulation problem. So far as I know, in order to build this model you shuold know the temperatures on the surface of the heat sink and the heat generation rate of your ALU. These will conjure up the concept of heat transfer coefficient associated with convection, a proportionality coefficient between the heat flux, Q/(AΔt), and the thermodynamic driving force for the flow of heat ΔT (in your problem). Considering radiation, you are also supposed to know the emissvity and absorptivity of your model, of course you know the Stefan-Boltzmann Constant 5.67*10exp(-8)  W/(m^2/K) ). So, S*h*(T_surf-T_ambient)+S*ε*σ*(T_ambient^4-T_surf^4)="The rate of change in energy storage", may be in the form of an integral (the heat sink consists of different materials).


By the way, there are  2 kinds of heat transfer types, convection and radiation, on the bounding surface . Hopefully, you may obtain 2 heat transfer coefficients associated with them, respectively, or a summation of them.

Hope that may help.

James_Wang

Thanks for your advices, courageddt! You are right, I am doing heat sink simulation. For the housing with complex shape I need calculate the heat transfer coefficient either through analytical way(using nusselt number and prandt nummer) or CFD. I am facing free convection and forced convection as well. Meanwhile I need consider the radiation effect(black housing). Because the FE Model has been built already with thermal Solid 92 element. Could you please tell me, can I or how should I define radiation directly in Ansys9.0 in my solid model? How can I run a forced convection in Ansys9.0, do I need a CFD simulation?
Sorry for my long questions. I am really a new comer with thermal problem.

Many thanks in advance!