Energy and exergy analysis of latent heat storage with heat pipe encased in phase change material

Abstract

Loop heat pipe (LHP) encased in phase change material (PCM) incorporated annular to catalytic converter (CC) is proposed to augment the performance of the “thermal energy storage” (TES). LHP are designed to extract surplus heat from the exhaust discharge, thereby reducing the amount of exhaust heat emitted into the atmosphere. A four-cylinder IC engine’s CC is considered with Mg 70 Zn 24.9 Al 5.1 , paraffin oil as PCM and working fluid for the heat pipe are evaluated. A comparative experimental investigation was performed considering two models for CC with and without heat pipe integrated in the TES for (i) distribution of average PCM temperature (ii) energy, exergy efficiency and distribution (iii) effectiveness (iv) instantaneous waste heat recovered during heat storage. Transient cycles at 2000 r/min with varying load conditions were run considering city drive conditions. Heat storage for CC with heat pipe encased in TES was found to be 35% faster, whereas discharge time for CC without heat pipe developed in TES was found to be longer. For melt fraction 1, maximum exergy efficiencies of 71% and 69% were observed for the TES unit with and without heat pipe. Heat pipes are observed to help extract a considerable amount of surplus heat from exhaust and reduce the exhaust gas outlet temperature released into the atmosphere by nearly 130 – 40°C under various load circumstances.