Experimental improvements of heat transfer in a latent heat thermal energy storage unit with embedded heat sources

Abstract

An experimental study was conducted in order to improve the heat transfer in a single layer latent heat thermal energy storage unit with embedded electrical heat sources. This study is motivated by the need to increase the performance of a more complex multi-layer latent heat thermal energy storage system used for smoothing daily electrical load profiles. In the first part, it is shown that melting from discrete heat sources may be substantially enhanced by a careful distribution and/or by activating the sources at different times. These strategies render the natural convection flows in the melt more efficient for melting the PCM and preventing overheating of the heat sources. In the second part of the study, passive air side heat transfer augmentation techniques are examined in order to improve heat recovery. It is found that augmented channels prolong the heat recovery period while maintaining the outlet temperature in a comfortable zone. Wire coiled channels proved to be very efficient for air flow Reynolds number Re above 1000. For Re=1700, the heat transfer coefficient increased by 190%, while the pressure drop increased by only 60%.