Packed bed regenerators using cascaded phase change materials : overcharging and possible solutions

• Main Authors: Khor, Jun Onn, Li, Yongliang, Romagnoli, Alessandro
• Other Authors: School of Mechanical and Aerospace Engineering
• Format: Conference or Workshop Item
• Language: English
• Published: 2018
• Subjects: Thermal Energy Storage; Packed Bed Regenerators; DRNTU::Engineering::Mechanical engineering
• Online Access: https://hdl.handle.net/10356/87932; http://hdl.handle.net/10220/46570
• Institution: Nanyang Technological University

In this paper, packed bed regenerators using different phase change materials cascaded in series for cold energy storage are investigated with specific focus on charging behaviour. Indeed, when one phase change material has significantly different thermodynamic properties than the others, or when flow rate of heat transfer fluid which contains cold energy to be stored is low, there can be an undesired scenario of overcharging certain phase change materials. This scenario subsequently leads to wastage of cold energy, especially when the phase change material meant for high grade cold storage is overcharged. Two solutions are suggested such as changing the encapsulation size of the affected phase change materials or increasing the storage capacity of the phase change material, or combining both of them. It is found out that increasing the storage capacity alone can solve the overcharging problem, with an improvement on the storage capacity of the regenerator. However, this increase in storage capacity also increases overall charge time of the regenerator. When incorporating both increase in storage capacity and encapsulation size of the affected PCM, the increment in storage capacity is less, but it brings an advantage of slighter increase in the overall charge time of the regenerator. It is also proven that in any of the cases, the efficiency in recovering or storing the high grade cold energy, is improved compared to the baseline cases.