Experimental comparison of the operation of PCM-based copper heat exchangers with different configurations

Abstract

Designing a heat exchanger/accumulator which can store a high quantity of heat in a brief period of time is one of the most important technological challenges. In this study, heat exchangers are designed for industrial processes with high heat recovery and storage rates where steam is used and the release of this steam to the atmosphere is cyclical and lasts for a short period of time. In order to recover and store the highest possible amount of energy from the steam, an efficient heat recovery and storage system is required. Phase change materials (PCMs) which allow storing large amount of energy in relatively small volumes could be used in thermal energy storage (TES) systems. However, low thermal conductivity of most PCMs causes long melting and solidification processes, especially when high energy recovery and storage rates are required, which leads to the development of complex geometries of heat exchanger (HX) and a significant increase in production costs. The aim of this study is to experimentally compare and assess the operation of two PCM-based copper heat exchangers (PCM-HX) with different geometrical parameters. This study focuses on the configuration of a PCM-HX which would ensure faster heat exchange and lower production costs. Two different configurations of fin-and-tube HX (denoted by PCM-HX1 and PCM-HX2) were analysed. Experimental investigation shows that both PCM-HXs achieve similar results but taking into consideration the complexity of production, it is concluded that the PCM-HX2 ensures better performance (PCM-HX2: melting time 8 min, solidification – 0.25 min; PCM-HX1: melting time 10 min, solidification – 1.25 min).