Ansys Fluent – Heat Exchanger (Shell and Tubes)

In a shell and tube exchanger one fluid runs through the tubes while the other flows around them inside the shell, and the heat passes through the tube walls. The quantities that matter are the outlet temperatures, the heat transferred, and the pressure drop on each side.

The modelling decision is conjugate heat transfer. The tube walls are solid cells that conduct, with fluid on both sides, so the interfaces need to be coupled walls rather than simple boundary conditions. Without that coupling, the exchange is imposed rather than computed.

Baffles are what make the shell side interesting and what makes the mesh harder: they force the flow across the tube bundle instead of letting it run straight through. Near the tube walls the thermal boundary layer must be resolved, so inflation layers sized from your target y+ matter as much here as in any aerodynamic case. The Y+ calculator gives you that first layer height.