Analysis of PCM Material in Thermal Energy Storage System

Abstract

A phase-change material (PCM) is a substance with a high latent heat storage capacity which on melting and solidifying at a certain temperature, is capable of storing and releasing large amounts of energy. Various PCM like Paraffin wax, sodium acetate tri-hydrate and phenolphthalein are considered which are used to absorb heat from the coolant water from the engine. The conduction and convection criterion of heat transfer enable the PCM to store this heat as latent heat. The amount of convection and temperature change brought about due to the heat flux has been simulated and studied in detail using GAMBIT and FLUENT . Increasing environmental pollution is an important problem observed during cold start of internal combustion engines. Cold start of internal combustion engines is characterized by various problems such as increase of fuel consumption resulting from heterogonous combustion, increasing concentration of toxic emissions, increase of lubricant viscosity and resistance to motion and thereby increase of load on the accumulator and starter resulting in increased vibration and noise. Developments of new devices that solve this problem are a necessity. Thermal energy storage system (TESS) is one such device. The TESS uses Phase Change Material's (PCM) latent heat storage capacity for pre-heating the internal combustion engine. The thermal energy storage device (TESD) works on the effect of absorption and rejection of heat during the solid-liquid phase change of heat storage material. The overall function of the TESS is dominated by the PCM. The PCM material should be selected considering the application and the working conditions. Depending on the applications, the PCMs should first be selected based on their melting temperature. Materials that melt below 288 K are used for storing coolness in air conditioning applications, while materials that melt above 363 K are used for absorption refrigeration. All other materials that melt between these two temperatures can be applied in solar heating and for heat load leveling applications. Gu et al (1) developed a heat recovery system using PCM to recover the rejected heat of air conditioning systems and produce low temperature hot water for washing and bathing. They concluded that the heat recovery system