Analytical modeling and thermal performance analysis of a flat plate latent heat storage unit. (October 2020)

• Record Type: Journal Article
• Authors: Ding, Chen; Niu, Zhiling; Li, Bingwei; Hong, Dongpao; Zhang, Zijun; Yu, Muchun
• Is Part Of: Applied thermal engineering. Volume 179(2020)
• Publication Date: 2020-10
• Subjects: Latent heat storage -- Phase change material -- Analytical model -- Thermal performance -- Flat plate -- Effective latent heat storage ratio; Heat engineering -- Periodicals; Heating -- Equipment and supplies -- Periodicals; Periodicals; 621.40205
• DOI: 10.1016/j.applthermaleng.2020.115722
• Languages: English
• ISSNs: 1359-4311

Abstract

Graphical abstract: The approximate analytical expression of the solid-liquid interface and the heat transfer fluid bulk temperature versus time for a flat plate latent heat storage unit was developed. Highlights: Analytical expression of the transient heat transfer fluid temperature distribution. Effect of thermal conductivity and geometric parameters on the thermal performance. The increase of PCM mass by lengthening the slab could improve thermal performance. A dimensionless design criterion is proposed to design the latent heat storage unit. Abstract: The thermal performance of a flat plate latent heat storage unit (LHSU) consisting of parallel flat plate slabs of phase change material (PCM) was investigated with analytical techniques. The approximate analytical expressions of the heat transfer fluid (HTF) transient temperature distribution and the time wise solid-liquid PCM interface location were developed by solving the energy conservation equations and were validated by comparing the present results with fully converged numerical predictions and analytical solutions in published literature. An index of effective latent heat storage ratio, Er, which was defined as the ratio of the actual amount of available latent thermal energy before HTF outlet temperature reaches a specified value to the total latent heat storage capacity, was proposed to evaluate the thermal performance of a LHSU. The effects of geometric parameters and the thermal conductivity of PCM ( kp ) on Er were investigated. The results show that the analytical model is valid as the Stefan number is less than 0.15. Moreover, Er increases with the rise of the given dimensionless HTF outlet temperature and the enhancement of kp, and decreases linearly with the increase of HTF channel height and PCM slab thickness, with an abrupt change in the derivative of Er at an inflection point. A dimensionless criterion was proposed to help design thermally efficient flat plate LHSU. Additionally, we found that increasing PCM mass by lengthening the PCM slab could significantly improve Er, while thickening the PCM slab would lead to the opposite trend. This investigation provides guidelines for the optimal design of a flat plate LHSU.