Performance prediction on ice melting process for cold energy utilization: Effect of natural convection

Abstract

Due to poor thermal conductivity of phase change material (PCM), applications of ice storage and cooling systems are hindered. To analyze the effect of natural convection on melting process for a horizontal shell-and-tube latent heat storage (STLHS) unit, the melting performance of STLHS unit with various endothermic source temperatures and eccentric directions is investigated by experiments and numerical simulation. Temperature distribution, liquefaction rate, and transient-overall heat transfer coefficient during the melting process are analyzed. Results show that circulation vortex formed by natural convection is a dominant factor that affects the transient-overall heat transfer coefficient. Total melting time of the STLHS unit is advanced by 41.8 % as the endothermic source temperature is increases from 279.15 K to 281.15 K. Influenced by density inversion and real physical properties of ice and water, melting tendency of the PCM shows opposite directions with the increase of endothermic source temperature. Time to total melting by raising the endotherm source by 5 mm is 45.4 % earlier than that lowers it by 5 mm at 281.15 K. Further, this analysis strategy provides theoretical guidance for the design of shell-and-tube ice storage units, which can be widely used for rapid cold energy extraction.