As moist gas enters a reciprocating compressor in the course of the operation of the compressor, heating of the gas depends on the degree of dryness of the gas and the rate of evaporation of the liquid droplets in the gas as well as on the coefficient of thermal conductivity of the moist gas and on the coefficient of heat transfer from the walls of the compressor cylinder to the gas. However, once the rotational speed of the compressor shaft reaches 300 min–1, the length of the gas intake process falls to one-tenth the length of the period of total evaporation of the droplets, hence the process of evaporation begins to exert a practical influence on the temperature of the gas. The gas temperature increases substantially due to the increase in the thermal conductivity coefficient of the moist gas and in the coefficient of heat transfer from the walls of the compressor cylinder to the gas. With a decrease in the degree of dryness of the gas from 1.0 to 0.6, preheating of the gas grows 7–8-fold, which leads to a reduction in the density of the gas in the filled work space of the cylinder and, as a consequence, to a decrease in the adiabatic efficiency of the compressor ηi by 14–16%, and this must be taken into account in the management of the production process.