Thermal energy storage optimization using composite foam-nano enhanced phase change materials

Abstract

A design of latent heat thermal energy storage (LHTES) unit for the rapid charging process of the nano-enhanced coconut oil inside an open-cell copper foam was proposed. A stream of hot liquid coconut oil was allowed to enter the thermal energy storage unit from the bottom and leave the unit from the top to accelerate the melting process. A heat transfer tube was placed inside the unit to melt the PCM layer and open a liquid film passage between the inlet and the outlet. The impact of design parameters such as porosity of copper foam, inlet PCM liquid pressure, hot inlet liquid inside the heat transfer tube, and volume fractions of nanoparticles was investigated on the charging time of the unit and its thermal behavior. The formation of the liquid PCM film over the heated tube is the key to fast charging. The key parameter in liquid film formation was the inlet velocity of hot liquid inside the tube. Increasing the inlet velocity by 2.5 times could reduce the thermal charging time by 2.5 times. Moreover, using nano-additives was not beneficial in this design since they could delay the liquid PCM film formation and the charging time.