Performance analysis of a packed bed latent heat thermal energy storage with cylindrical‐shaped encapsulation

Abstract

Summary In this work, a numerical model of a vertical cylindrical packed bed latent heat thermal energy storage (PBTES) system filled with cylindrical‐shaped encapsulations is developed. Two energy equations with a non‐equilibrium heat transfer model are employed to analyze the transient variation of heat transfer fluid (HTF) and encapsulated phase change material (PCM) considering the filler material as a porous medium. An enthalpy‐porosity technique is used to model the melting and solidification of PCM inside the capsule. The effects of the shape of the encapsulation, the aspect ratio of cylindrical encapsulation, the porosity of the storage system, HTF flow rate and encapsulation material are studied using the validated numerical model. For the same volume of encapsulation, the heat transfer rate and the thermal efficiency are found to be higher for the spherical encapsulation as compared to the cylindrical encapsulation. The thermal efficiency and the heat transfer rate of the storage system increase with the increase in the aspect ratio of the encapsulated PCM cylinder. With an increasing flow rate of HTF through the packed bed, the heat transfer rate and thermal efficiency improve. The PBTES with higher thermal conductive encapsulation material is more efficient and has a higher HTF temperature at the outlet during the discharging operations. The stabilization factor (SF) is introduced to assess the stabilization performance of the PBTES. The SF is lowest for the cylindrical encapsulation of aspect ratio of 4/3, the porosity of bed of 0.33 and the lowest HTF flow rate of 7.05 L/min considered in this study.

Variable PCM Density-based Numerical Model for Packed Bed Latent Heat Thermal Energy Storage

“…Most of the PCMs have lower thermal conductivity, which results in a lower heat transfer rate. Various researchers reported the heat transfer improvement method from PCM to HTF, such as encapsulation of PCM [7][8][9], and the addition of metal matrix and fins [10]. The encapsulation of PCM is one of the heat transfer enhancement methods.…”

Noticeable improvement in morphological characteristics and thermal reliability of n‐octadecane@ SiO 2 nanocapsules for thermal energy storage

“…For instance, the thermal performance of a webbed tube heat exchanger using PCM was numerically investigated, 6 the solidification of PCM in the triple-tube latent heat TES system was examined, 7 and a numerical model for the packed-bed TES system was developed. 8 In general, organic phase-change materials (PCMs) are widely used owing to their excellent thermal performance and compatibility with various materials. 9 Paraffin wax, an organic PCM, is mainly composed of straightchain n-alkanes.…”

“…Because phase‐change material (PCM) can store a large amount of thermal energy in the phase‐change temperature, various studies have been recently focused on PCM‐based heat exchanger applications. For instance, the thermal performance of a webbed tube heat exchanger using PCM was numerically investigated, 6 the solidification of PCM in the triple‐tube latent heat TES system was examined, 7 and a numerical model for the packed‐bed TES system was developed 8 …”

Perspectives on Low-Temperature Packed Bed Latent Heat Storage Systems

“…The traditional PBTES is based on sensible heat transfer and is therefore limited by a low energy density and temperature stability (Mawire et al, 2020). Compared with the traditional system, a packed bed latent heat storage (PBLHS) system based on phase-change materials (PCMs) (Wang H. et al, 2018;Wang J. et al, 2018) offers advantages such as a higher energy density, higher temperature stability, and few safety issues Kumar and Saha, 2021;Wang et al, 2021) and therefore is considered a promising solution for thermal energy storage (Yang et al, 2017;Zhang et al, 2020;Grabo et al, 2021).…”