Abstract— <p>The paper examines the stationary processes of heat and moisture transfer during condensation cooling of gases by a liquid phase on trays of various designs in scrubber coolers. The efficiencies of the processes, heat balance equations, and the number of transfer units in the gas phase are considered. For calculation of the thermal efficiency of gas cooling, well-known expressions from mass transfer theory are used, taking into account the hydrodynamic structure of the flows, as well as a criterial expression for the Sherwood number. Examples of calculations and graphical dependencies of thermal efficiency on gas velocity are provided for different types of trays (perforated, valve, jet, and others) during cooling of air with water. A one-dimensional differential heat transfer equation is presented, whose solution enables for the consideration of non-uniformity in the gas velocity profile and the liquid level gradient along the tray, enabling the calculation of process efficiency. The study presents the dependencies of temperature fields and thermal efficiency for perforated and valve trays It is shown that a non-uniform gas velocity profile, caused by the liquid level gradient, reduces thermal efficiency.</p>