Performance of a new packed bed using stratified phase change capsules

This article presents a numerical study of a new packed bed using a stratified phase change material (PCM). The PCM is injected into polycarbonate spheres as phase change capsules. Water is used as heat transfer fluid (HTF) for charging or discharging thermal energy to the PCM. Three kinds of paraffin that have different melting points are used as the PCM and placed in the packed bed at different heights. The PCM at the higher melting temperature is placed nearer to the hot water inlet. The numerical calculation of HTF is based on the one-dimensional Schumann's model, while the temperature of the PCM is simulated using the apparent heat capacity method. Both charge and discharge processes of this new stratified packed bed have been studied. The effects of HTF average velocity and inlet temperature have also been investigated. Both the energy and exergy performance are compared with those of the packed bed using only one kind of PCM. The comparison results indicate that this new stratified packed bed has an advantage over traditional packed bed in terms of energy and exergy.