Tube heat exchanger

Using the shell side allows the two phases to be separated, for example by enhancing gas-liquid separation at the lower point and exhaust gas release at the higher point.

What was said upstairs isn’t very reasonable. When the phase-transformed gas flows through the tube side, even after a temperature drop, outlets for gas and liquid can still be provided at the exit; there is no factor that prevents the separation of the two phases. If the poster is referring to tube-in-tube heat exchangers, choosing to use gas in the shell side is done because, under such operating conditions, liquid refrigerant is usually used on the tube side. In this case, the volumetric flow rate of the liquid is relatively higher than that of the gas on the shell side; therefore, multi-shell-side designs are commonly used. The overall heat transfer coefficient in such cases is higher when gas is used on the shell side and liquid on the tube side (note that it’s the tube side – things change if internal finning or other elements for enhancing heat transfer on the tube side are used). Hence, it’s common to choose to use gas on the shell side