Condensation of saturated vapours on compression and estimation of minimum suction superheating

A very simple criterion is derived to determine whether pure saturated vapours will be superheated or partially condensed when compressed, taking the isentropic efficiency of the compressor into account. The only fluid information that is required is the compressor suction (saturation) temperature, and the ideal gas heat capacity and enthalpy of vaporisation (latent heat) at that inlet temperature. In cases where partial condensation occurs, this approach allows for the estimation of minimum degrees of superheat required prior to compression to ensure that no liquid formation takes place. The approach relies on conditions where ideal gas behaviour can be assumed; as a rule of thumb, the method should not be applied at T/Tc > 0.6.

► A simple criterion is given to determine if a compressed saturated vapour condenses. ► Equations are given to estimate the degree of superheating to avoid liquid formation. ► The compressor's isentropic efficiency is taken into account. ► Examples are provided, and comparison is made with rigorous simulation.