Entropy and thermal performance analysis of PCM melting and solidification mechanisms in a wavy channel triplex-tube heat exchanger

Abstract

This paper aims to perform the entropy analysis and thermal performance evaluation of a wavy-channels triplex-tube latent heat storage heat exchanger (LHSHE) during melting and solidification mechanisms. The system with different wave amplitudes was examined for different temperatures and Reynolds numbers of the heat transfer fluid (HTF). Water is passed in the inner and outer tubes in opposite directions and the PCM is placed in the middle tube. The heat exchanger was analyzed based on the temperature, liquid fraction and velocity of the PCM as well as thermal (ST‴) and frictional (Sf‴) entropy generation rates. The results show that for a higher wave amplitude, shorter melting and solidification times are achieved. Both frictional and thermal entropy generation rates increase to the maximum values and then decrease during the melting and solidification. The frictional entropy generation rate reaches almost zero quickly during the solidification. For both melting and solidification, the magnitude of ST‴ is significantly higher than Sf‴ in the phase change problem. The maximum values of ST‴ are 0.05 and 0.13 W/Km3 for the melting and solidification mechanisms, respectively, for the dimensionless wave amplitude of 0.3. The results show the crucial role of entropy generation on the performance of the LHSHE.