setting a reference temperature for htc and nusselt
There are a couple of questions existent on the forum on this mater, but do not discuss temperature.
L03_ForcedConvection.pdf for Fluent Heat transfer pdfs does talk about it, but in that case, the bulk temperature itself is given as the reference temperature.
Could you please slightly elaborate, perhaps by giving a hypothetical example yourself, on how is the reference temperature to be given for nusselt calculations, lets say if I have a constant heat flux wall bc, instead of the T_wall bc specified in the above pdf.
As h_eff = q/ (T_wall - T_ref), and following the instructions of aforementioned pdf, I had set my reference temperature equal to bulk temperature at periodic bc, however this just gave a nusselt value (area-weighted average-on wall), twice of what I sould get from an emperical sieder-tate equation for a smooth pipe.
So the question is, because the pipe is smooth, and the reynolds turbulent, I should be able to get within 10% of an emperical correlation, but that is not the case, because the reference value setting for the htc, and hence the nusselt, needs an understanding.