For there is no mixing of fluids in heat exchanger, my confusion is if i do not invoke the multiphase model, only one phase is assumed in Fluent. Actually, there are two fluids (gas and liquid) in different channel. How to define those two different phase in FLUENT without invoking mulitphase model? Could you explain it in detail? Thank you very much.

if fluid lies in incompressble domain. Simply apply velocity inlet boundary condition and outflow boundary condition with their appropriate weighting factors

Ejaz Ahmed