Hybrid and conservative temperatures
 

I was running a Laminar flow simulation. Since the flow is laminar I did not consider the boundary layer resolution and I proceeded with tet mesh with out any prisms.

There are heat sources inside the domain and from the simulation I see that the hybrid and conservative values of the surface temperatures of the heat sources differ around by 100 [C].

So I wonder if I should have prism layers in the mesh even if the flow is laminar.

Could some one please suggest upon this

Yes, you should have prisms. The mesh needs to resolve solution gradients. Prisms are just an efficient way to resolve the strong gradients that typically occur near walls. Just because the flow is laminar you will still have gradients to resolve near the wall, so you should still use prisms.