how to generate prism mesh in tube-shell exchanger?
 

how to use ansys meshing to generate prism mesh in tube-shell exchanger?
following picture is generated by ansa.it is done by my friend.

Use your RMB (Right Mouse Button) on Mesh, and select inflation. There, first select the volume and secondly the walls you want to inflate.

This is a very basic question. Did you do any tutorial?

I'm sorry; maybe I didn't describe it clearly.
First, I emphasis the volume mesh is prism, inflation is hex. I want to use Mutizone method, and found its failure

Wouldn't it be better to have hex in the volume and for boundary layer, either hex or prism?

Given the complexity and size of your model, you would be better of using Poly-hexcore meshing in Fluent meshing, you are spending too much of you time in ansys meshing.

But generally, a combination of inflation and multi-zone should help you make this mesh. But again, it would be time taking and complex.

I think it should be possible using Multizone, but your geometry should be very clean. The mesher prefers sweepable bodies. It you don't have them, then you'll have a hard time.
Also, dedicated meshers like ANSA can generate better meshes than the general purpose mesher in Workbench.