Performance criteria for a heat exchanger

摘要

The performanc eof heat exchangers is usually measured by the effectiveness as defined by Kays and London (1984).The effectiveness is the amount of heat actually transferred diveided by the maximum amount of theoretically transferable heat.However,this criterion tis not adequate,because it does not take into account quality losses of the transferred heat and pressure drops of the fluids.A high effectiveness is no guarantee that we have a good performance of hte heat exchanger.Therefore a new criterion is introduced,which is not only basedf on the first,but also ont he second law of thermodynamics:the rational efficiency.An equation is derived which includes the effectiveness to calculate the rational efficiency.An example hs bene included in which both performance criteria are ocmpared.