Why does negative heat flux come?
 

Hi Guys
I am dealing with a conjugate heat transfer problem. The flow is basically "flow between two parallel plates" and those parallel plates have some thickness. I gave heat flux BC on one of the walls of these plates. But I get negative heat flux in the solid region when it is trying to solve. What could be the problem??

Thnx

Probably nothing is wrong (other than the user not understanding sign conventions).

Negative heat flux typically means the heat flux is in the direction opposite of the direction assumed to be positive when the equations were derived.