[Shabi1992]

I want to calculate Nusselt number in a canal with constant wall temperature. I've tried many times, and the results do not match previous works.*
*I need to find Nu number on the wall ,so I draw a line on the top of the canal wall and calculate wall heat transfer coefficient, but based on hD/k it is*unreasonably high. I write this expression Nu=(q*D)/((Tw-Ti)*k), as well which
q= heat flux
Tw=wall temperature
Ti=inlet temperature
D=hydraulic diameter
k=thermal conductivity

but the results are difference again.

Does anyone have any experience calculating Nu number*in CFX?
I would be thankful if anyone can help.