Conjugate heat transfer-Rib turbulated cooling
 

Hello all,

I am working on a CHT problem, regarding rib-turbulated cooling. There are no convergence issues with the simulation. The convergence criteria was 1e-08. The temperature contours are coming absolutely fine. But for the Nusselt number contour, there are several locations with negative value of Nusselt number. I have given the correct values for reference values.
Constant heat flux boundary condition was applied for all the four walls.

Please let me know, as to what can be the reason for the negative values of Nusselt number (the grid quality is good).

Regards
Avinash