variable Thermal conductivity in Nusselt
 

Hi
I have laminar nanofluid in a pipe under constant heat flux. I need h.d/k to find the local nusselt number. the thermal conductivity is variable along the pipe. is there any method in ansys fluent / post CFD to calculate the Nusselt along the pipe versus location? (like a xy result)
Thanks
Navid


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First you need to figure out how to calculate kref(x,y) and Tref(x,y), and in my opinion these are much more difficult problems.

Assuming you have kref and Tref locally, you can define new field functions inside Fluent or inside CFD post and apply the correction factors. You could also do this externally in excel or your favorite programming language after you have exported the necessary values.

However, there's not a simple automatic way to do it. I.e. you can't just tell Fluent to use a reference temperature field and reference conductivity field. Your options in the reference values are limited.