Comparative study between heat pipe and shell-and-tube thermal energy storage

Abstract

• Comparison of different latent heat thermal energy storage systems with heat pipes. • Assessment of replacing a heat transfer fluid piping system by heat pipes. • Heat pipes provided a uniform melting process. • The phase change material took control over the heat pipe operation cycle. This paper experimentally evaluates the implementation of heat pipes in latent heat thermal energy storage systems. The well-known performance of heat pipes as a heat transfer technology makes them great candidates to be used as heat exchangers. However, previous studies compared their efficacy against solid metal rods, where heat pipes clearly succeeded. Therefore, the objective of this study is to experimentally evaluate the advantages of using heat pipes instead of a common shell and tubes system, during charging processes. In particular, five latent heat thermal energy storage systems were tested. One based on the shell and tubes, and the remaining four based on heat pipes. The experiments were conducted at constant heat transfer fluid temperature and flow rate, and the results were analysed from the temperature, heat transfer, and visual point of view. The results show that in heat pipes systems the phase change material melts homogeneously through all the storage container. However, the shell and tubes tank performed the charging process in 25 min while the fastest heat pipe one took 40 min for it. On the other hand, in the shell and tubes configuration melt from the heat transfer fluid inlet towards the outlet. Moreover, systems with more heat pipe surface inside the heat transfer fluid collector provided higher power rates. Comparing the best and the worst heat pipe storage tanks during the first 30 min, the heat transfer rate increased over 40%. But the storing material low conductivity cushioned those high heat transfer rates.