Heat exchanger performance for latent heat thermal energy storage system

Abstract

An experimental and theoretical study was carried out to investigate the heat transfer in a component of a low temperature thermal energy storage (TES) system using the latent heat of fusion of a phase change material (PCM). The heat storage container is a double pipe heat exchanger where the energy source fluid (hot water) flows through the inner tube, while the heat sink (storage PCM) fills the annulus gap. The tested phase change material is the paraffin wax of melting temperature of 50°C. Measurements were made of the temperature change of the hot water as well as of the paraffin wax. The heat transfer rate and the accumulative energy stored as a function of time is presented for different hot water flow rates and inlet temperatures. An analytical model is developed for the prediction of the storage heat transfer rate and accumulative energy. The predictions of the model are compared with experimental results and show good agreement. The developed model is also used to study the effect of convertion in the molten zone, initial PCM subcooling, and heat exchanger dimensions on heat transfer rate and accumulative energy.