A review of materials, heat transfer and phase change problem formulation for latent heat thermal energy storage systems (LHTESS)

This paper reviews the development of latent heat thermal energy storage systems studied detailingvarious phase change materials (PCMs) investigated over the last three decades, the heat transfer andenhancement techniques employed in PCMs to effectively charge and discharge latent heat energy andthe formulation of the phase change problem. It also examines the geometry and configurations of PCMcontainers and a series of numerical and experimental tests undertaken to assess the effects ofparameters such as the inlet temperature and the mass flow rate of the heat transfer fluid (HTF). It isconcluded that most of the phase change problems have been carried out at temperature ranges between0 8C and 60 8C suitable for domestic heating applications. In terms of problem formulation, the commonapproach has been the use of enthalpy formulation. Heat transfer in the phase change problem waspreviously formulated using pure conduction approach but the problem has moved to a different level ofcomplexity with added convection in themelt being accounted for. There is no standardmethod (such asBritish Standards or EU standards) developed to test for PCMs, making it difficult for comparison to bemade to assess the suitability of PCMs to particular applications. A unified platform such as BritishStandards, EU standards needs to be developed to ensure same or similar procedure and analysis(performance curves) to allow comparison and knowledge gained from one test to be applied to another.