Performance of a finned, latent-heat storage system for high temperature applications

A cost effective thermal storage system is required for the widespread application of the parabolic-trough solar thermal power generation technology. Such systems currently employ the sensible two-tank thermal storage system. The use of phase-change storage systems offers higher storage density and efficiency. However, due to the low thermal conductivity of suitable commercially-available phase-change materials (PCMs), heat transfer enhancement is required. Amongst heat transfer enhancement methods in latent-heat storage systems, the use of fins is the most practical for high-temperature applications. The heat transfer performance during the charging and discharging of a finned, latent-heat storage system was studied using CFD simulations for three commercially-available PCMs. During charging, natural convection plays a dominant role in the heat transfer. The quasi-steady effective heat transfer coefficient was found to depend on the heat transfer fluid (HTF) mass flow rate and the thermo-physical properties of the PCMs, but independent on the driving temperature difference. Although convection plays a role at the beginning of discharging, the main mode of heat transfer during the process is pure conduction. In this study, correlations that can be used for estimating the heat transfer rates during charging and discharging of a finned, latent heat storage system, using synthetic oil as the HTF, were developed.