In order to investigate the influences of air saturability on the heat transfer effect, this paper uses the numerical simulation method to calculate the effect on total heat exchange, entransy dissipation, entransy dissipation thermal resistance and heat exchange efficiency when air changes delay isotherm, isenthalpic and isobume near the saturation line. It is found that when the gas changes along the three lines approach to the saturation line, the thermal dissipation of the entransy dissipation always decreases, and the total heat exchange efficiency increases.