Comparative study of heat transfer enhancement in a latent heat thermal energy storage system using mild steel and stainless steel spherical PCM containers

Abstract

Thermal energy storage (TES) systems that employ latent heat storage materials have recently received more consideration because of their large heat storage volume and isothermal characteristics during heat storage and heat discharge. The phase change material (PCM) in the LHTES system accumulates large amounts of energy to a slight temperature extent by altering its phase. However, the low thermal conductivity of PCM is a major issue while using it in the LHTES system. Solid metal fins are used in PCM containers to surge the heat transfer rate and decrease the melting time. In this study, the experiments were performed under experimental conditions controlled using different mass flow rates of 2 L/min, 4 L/min, 6 L/min, and the heat transfer fluid (HTF) inlet temperature for the storage process is 70 ℃. The characteristics of the LHTES system are analyzed to accumulate the thermal energy in the spherical PCM container with and without solid internal fins. In this study, the granulated paraffin wax with a melting temperature of 61 ℃ was used as PCM. The water is used as the HTF to transfer the thermal energy from the source to the TES tank. The changes in temperature differences have been experimented with different HTF flow rates with all configurations of PCM containers to examine the temperature distribution. While increasing the flow rate between 2 and 6 L/min, we note that loading time is decreased by 38.46 % and 37.50 % for the case of stainless steel with fins and without fins spherical containers. The charging time is fallen by 36.36 % and 35.71 % while increasing the flow rate between 2 and 6 L/min for the case of mild steel with fins and without fins spherical containers. The cumulative heat stored is higher for fin configuration than no fin configuration spherical PCM containers.