Second law thermodynamic analysis of imbalanced counter flow heat exchanger for energy conservation

Abstract

Entropy generation of imbalanced counter flow heat exchanger is analyzed to know the thermal behavior effects such as entropy generation minimization and exergetic efficiency. The analysis of first law which does not considers different irreversibilities such as transfer of heat, drop in fluid pressure and mass flow streams unbalance is possible from second law of thermodynamics studies. In this analysis the parameters which are considered are length to diameter dimensions of heat transfer equipment tube, fluid streams capacity ratio, Reynolds number of fluid and type of fully developed fluid flow. To understand the behavior of heat exchanger the heat capacity rate of heat exchanger’s maximum value is changed for both cases of hot stream and cold stream. Optimum heat exchanger geometrical dimension namely length-to-diameter ratio can be obtained from the second law analysis corresponding to lower total entropy generation and higher second law efficiency which leads to energy conservation. Accordingly, for the minimum entropy generation and maximum exergetic efficiency resulted, the optimum length-to-diameter ratio are obtained for different cases considered.