Nusselt number increase in laminar flow

[TaiwoOni]

This is what I read: "In turbulent flow the Nusselt number increases as the Reynolds number increases. This is due to increase in turbulent intensity as the Reynolds number increases resulting in more destruction of the boundary layer."
My question is this: In a laminar flow there is no turbulent intensity. So, why does the Nusselt number in laminar flow increases as the Reynolds number increases?

 

[25362]

May be page 2 on the attached link may offer you the needed answer:

http://web2.clarkson.edu/projects/subramanian/ch302/notes/Convective Heat Transfer 1.pdf

 

[ione]

As you should know, Reynolds number increases as fluid velocity increases and/or as fluid viscosity decreases. These two factors (velocity increase and viscosity decrease) both enhance heat transfer as they promote higher rates contacts between “portions” of fluid, which are at different temperatures, in different sites (locations). You should study further the velocity boundary layer and the thermal boundary layer concepts and the strict parallelism that exists between them.