Analysis of Natural Convection During the Melting Process of Hydrogenated Palm Stearin for Use as Phase-change Material

There are three main alternatives for the improvement of heat transfer in phase change materials (PCM) such as the use of additives, support matrices and customized designs for heat exchangers. The first two alternatives imply incurring additional material costs, as well as a decrease in the specific heat storage capacity by using components that remain solid during the process. The present work therefore sought to study the effect of the use of a coil shell heat exchanger with a square cross section on natural convection during the melting process of hydrogenated palm stearin. Three different sections of the profile called square profile, U-profile, and L-profile and two types of material, copper, and stainless steel, were studied. A test bench was built with a capacity of 5 kg of this PCM, implementing a hot water recirculation system with flow and temperature measurement and including 9 temperature sensors inside the PCM. The melting process was conducted by recirculating water with a temperature of 75° C and a flow rate of 2 L/min. The results show a marked effect of natural convection on the melting process, presenting characteristic profiles for this phenomenon. It was found that the highest temperatures are recorded in the upper part of the PCM and that the heat transfer in the solid material is appreciably low. The results allow us to identify for each profile, the zones in which heat transfer is relatively high because of natural convection and those zones that require the use of additives or support matrices. It is therefore expected to contribute to the design of more efficient and lower commercial cost configurations.