Thermo-mechanical analysis of microcapsules containing phase change materials for cold storage. (1st February 2018)

• Record Type: Journal Article
• Authors: Yu, Qinghua; Tchuenbou-Magaia, Fideline; Al-Duri, Bushra; Zhang, Zhibing; Ding, Yulong; Li, Yongliang
• Is Part Of: Applied energy. Volume 211(2018)
• Page Start: 1190
• Page End: 1202
• Publication Date: 2018-02-01
• Subjects: Phase change materials -- Microencapsulation -- Solidification -- Shell buckling -- Cold storage; Power (Mechanics) -- Periodicals; Energy conservation -- Periodicals; Energy conversion -- Periodicals; 621.042
• DOI: 10.1016/j.apenergy.2017.12.021
• Languages: English
• ISSNs: 0306-2619

Abstract

Highlights: Thermo-mechanical model is established for microencapsulated PCMs for cold storage. Embedding Al2 O3 nanoparticles into MF shell increases its resistance to buckling. Young's modulus or thickness of shell can be predicted according to buckling mode. The condition for avoiding buckling is proposed to improve the mechanical stability. Microencapsulated PCM slurries have higher energy storage capacity than packed beds. Abstract: Microencapsulated phase change material slurries (MEPCMSs) offer a potentially efficient and flexible solution for cryogenic-temperature cold storage. In this paper, the phase change material (PCM) microcapsules prepared to form MEPCMSs for cryogenic-temperature cold storage consist of Dowtherm J (DJ) as core material and melamine formaldehyde (MF) as primary shell material. DJ is an aromatic mixture with diethylbenzene as the main component. Composite shell materials are adopted to avoid cracking by adding aluminium oxide (Al2 O3 ) nanoparticles or copper (Cu) coating into/on MF shell. In order to explore the heat transfer behaviour and mechanical stability of the microcapsules during the solidification process of PCM, a thermo-mechanical model is established by taking into account of energy conservation, pressure-dependent solid-liquid equilibria, Lamé's equations and buckling theory. Based on the proposed model, the effects of shell thickness, shell compositions and microcapsule size are therefore studied on the variations of pressure difference, freezing point, and latent heat. The cause of shell deformation is clearly explained and the shell buckling modes are predicted using the model, which agree well with the experimental observations. The critical core/shell size ratios of avoiding buckling are proposed for the microcapsules with different compositions. Simultaneously incorporation of Al2 O3 nanoparticles and Cu coating into/on MF shell can markedly enhance the resistant to buckling. In addition, special attention is paid to cold energy storage capacity of MEPCMSs, which has considerable superiority compared to packed pebble beds.