Dear CFD staff I want to calculate Nu_local and Nu_avarage numbers for 3D ractangular duct with bottom side is heating with constant heat flux. And l would to find Bulk tempareture in this side. Thank you very much for help me emad

as i believe you r concerned with convection coefficient.

u can use emperical relation for the calculation of Nu,

like, for calculation of heat transfer in fully developed turbulent flow in smooth tubes is reommended by dittus and Boelter (Heat Trasfer, J P Holman, Eight SI Metric Edition, chapter 6, page 286)

Nu=0.023*Re^0.8 * Pr^0.4 ( for heating fluid)

there are many more emperical relation for these type of problem

so, when u have Re, Pr u can calculate Nu, by using Nu u can calculate h and using

Q=m*cp*(T1-T2)

u can calculate bulk temp.

if u r still not satisfy and only want to solve it on fluent then i must advise u to first solve it analatically and then solve the problem computationally and verify ur data. then solve the actual problem. in this way u will be confidient to solve and can justify ur results

thanks for reply Dear Sayed Shabbar I want to calculate Nu by using fluent using this eqation Nu=q*s/Tw-Tb),Tb:Bulk temp. on one side for rectangular duct. Thank you very much emad