Experimental studies on heat transfer characteristics of water based PCM composites for cool thermal energy storage applications

Abstract

Building sectors consumes nearly 40% of world energy consumption, out of which a major portion is being utilized for space cooling / heating applications. Usage of refrigeration and air-conditioning system involves a large quantity of refrigerants, leading to severe environmental degradation. There has been a pressing need to reduce the energy usage and conserve the environment without compromising the desired comfort conditions. Cool thermal energy storage systems (CTES), is one of the most appropriate methods, utilizing phase change materials (PCM) as a storage medium for the effective thermal management of buildings. An extensive literature survey has been carried out on various methods of heat transfer enhancement in the PCMs by passive methods. Water is being used as a potential PCM in the CTES systems owing to its high latent heat, availability and ease of handling. However, the existence of sub-cooling demands a lower operational temperature of the evaporator, consuming an additional energy of 3-4 % per degree temperature drop. Considering the above challenges in augmenting the energy efficiency of the CTES system, this research work aims to develop water-based composite PCMs (CPCM) with different additives and investigate their heat transfer characteristics in a spherical encapsulation during melting and solidification. First step of the experimental study was the selection of suitable additives compatible with the base PCM. Four different additives, namely, sodium chloride (soluble salt), D-Sorbitol (nucleating agent), Natural Graphite Flakes (NGF) (microparticles) and Graphitized Carbon Mesoporous (GCM) (nanoparticles) were selected. newline