A comparison between the entropy generation in terms of thermal conductance and generalized thermal resistance in heat exchanger analyses

Abstract

This paper reports the comparison on the applicability between the concepts of entropy generation in terms of thermal conductance and generalized thermal resistance to analyzing heat exchangers. Six typical two-stream heat exchangers and one three-stream heat exchanger are analyzed. When the heat capacity flow rates of the discussed heat exchangers are fixed, the minimum generalized thermal resistance always corresponds to the maximum heat exchanger effectiveness, while the minimum entropy generation in terms of thermal conductance does not always. When the heat capacity flow rates of the discussed heat exchangers are not fixed, smaller generalized thermal resistance always leads to larger heat transfer rate, while smaller entropy generation in terms of thermal conductance does not always. Therefore, the concept of generalized thermal resistance is more appropriate than the concept of entropy generation in terms of thermal conductance for describing the performance of the discussed heat exchangers.