Determining the Efficiency Ratio of a Heat-Exchange Apparatus

The author has proposed the general approach to determining the efficiency ratio of heat-exchange apparatuses with different schemes of motion of the heat-transfer agents on the basis of taking account of their final equilibrium temperature. A procedure has been developed to calculate this temperature for a cocurrent-flow scheme of motion of the heat-transfer agents. The proposed approach makes it possible to consistently determine and to correctly compare the efficiency ratios of heat-exchange apparatuses in counterflow, cocurrent flow, and crossflow of hot and cold heat-transfer agents. The author has given results of calculating the efficiency ratios of heat-exchange apparatuses used in the production of liquefied natural gas. It has been shown that the maximum operating efficiency of a heatexchange apparatus is attained with evaporation of the cold heat-transfer agent (coolant), which is characteristic of the processes of liquefaction of gases.