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hvem10 October 28, 2009 12:54

Conjugate heat transfer problem
 
Dear All,

I have a problem where I have a fluid surrounded by different solids and want to solve the heat transfer in the solids. The solids are surrounded by still air and I need to specify the outer boundary as Convection and give the Heat Transfer Coefficient. I can find different normal values by searching but I can see that I get different results depending on which value I use :( The higher heat transfer coefficient I use the more heat flux out of the outer boundary. I don't know what the heat flux should be, but want to find out. How do I determine the correct heat transfer coefficient.
Thanks in advance

Volker P. October 29, 2009 09:08

Quote:

Originally Posted by hvem10 (Post 234379)
Dear All,

I have a problem where I have a fluid surrounded by different solids and want to solve the heat transfer in the solids. The solids are surrounded by still air and I need to specify the outer boundary as Convection and give the Heat Transfer Coefficient. I can find different normal values by searching but I can see that I get different results depending on which value I use :( The higher heat transfer coefficient I use the more heat flux out of the outer boundary. I don't know what the heat flux should be, but want to find out. How do I determine the correct heat transfer coefficient.
Thanks in advance

So you are dealing with a free convection boundary. Heat transfer coefficient for free convection problems of horizontal or vertical plates can be found in several textbooks or handbooks (e.g. VDI Wärmeatlas).

Typically you' ll find values of about 1 up to 10 W/m2K for air and typical temperature gradients.

If you need a more exact value, see textbooks or: Maybe you can enlarge your modell and include the "outer heat transfer" into your model and convert it to an inner one..

hvem10 October 29, 2009 18:31

Dear Volker,
Thanks for your reply. I have been looking in text books, but my geometry is a bit out of the range of standard examples. But I wanted to be sure that I had not overlooked any smart approach, so thanks for the reply. I have now extended the domain such that I have the surrounding air included. I did find a heat transfer coefficent on 8, whcih is within the range you mentioned.
Thanks


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