Experimental and numerical investigation of heat transfer in a channel with multiple phase change materials (PCMs)

Abstract

In this study, the thermal performance of an air-phase change material (PCM) unit used in free cooling applications was examined experimentally and numerically by Comsol finite element simulation software. Effects of the air inlet temperature, velocity and also PCM configuration on the efficiency of the air-PCM unit were investigated. Experiments were performed on PCM unit, which is a channel including PCM plates inside and exposed to medium air entrance from one side. The air in contact with the plates inside this unit is cooled and contributes the room temperature to decrease. The experimental work was carried out at two different ambient temperatures in a well-insulated room. Three different configurations of paraffin-based pure RT22HC and RT25HC were studied. Effects of air inlet temperature and velocity on the heat transfer, channel outlet temperature, performance of the air-PCM heat exchanger, cooling power of the system and also total amount of heat absorbed by the PCM were investigated. The initial temperature of the PCMs is 16 ᵒC and experiments were carried out for two different average inlet temperature values (27 and 29 ᵒC) and two different average velocities (1.3 and 1.8 m/s) of the air at the channel entrance. According to the results, it was concluded that the air inlet temperature and air inlet velocity have a substantial effect on the thermal performance of the air-PCM unit. It was observed that the melting time decreased and the channel outlet temperature increased with the increase of air inlet temperature and velocity. 2 ᵒC increase of in the inlet temperature increased the total amount of heat absorbed by PCMs by 31%, while an increase of the inlet velocity by 0.5 m/s increased it by 16%. The results revealed that the increase of the inlet velocity and with the inlet temperature increased the thermal energy absorbed by 44%. In addition, it was observed that the average efficiency increased by 37% with 2 ᵒC increase of inlet temperature and 0.5 m/s decrease in the inlet velocity.