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3rd Thermal and Fluids Engineering Conference (TFEC)

ISSN: 2379-1748

A core-shell structured PCM with Na2SO4 encapsulated by SiO2 for high temperature thermal storage

Xiaodong Wu
Department of Civil and Architectural Engineering, University of Wyoming, Laramie, WY 82071, USA; Jiangsu Collaborative Innovation Center for Advanced Inorganic Function Composites, Nanjing Tech University, Nanjing 210009, China

Maohong Fan
Department of Chemical and Petroleum Engineering, University of Wyoming, Laramie, WY 82071, USA

Xiaodong Shen
Jiangsu Collaborative Innovation Center for Advanced Inorganic Function Composites, Nanjing Tech University, Nanjing 210009, China

Gang Tan
Department of Civil and Architectural Engineering, University of Wyoming, Laramie, WY 82071, USA

DOI: 10.1615/TFEC2018.ens.022311
pages 621-624


KEY WORDS: Phase change material, Encapsulation, Leakage, High temperature, Thermal storage

Abstract

In latent heat thermal storage, macro- or microencapsulation of phase change materials (PCMs) can benefit PCM performance. This work proposed a novel chemical method for microencapsulation of inorganic PCM for high temperature thermal storage. This method encapsulates Na2SO4 (PCM) with SiO2 shell via the sol-gel technique. The SiO2 shell is a fire-resistant material and can effectively inhibit the liquid leakage during solid-liquid phase change process. Comprehensively considering the thermal conductivity, thermal stability, melting temperature, and latent heat, the silica mass fraction has been optimized at 5.4% of the composite. In this encapsulation, silica particles were observed decorated on the surface of large Na2SO4 particle and perfect core-shell structures were obtained for the nano-size Na2SO4 particle. The thermal conductivity of the encapsulated Na2SO4@SiO2 has been enhanced by 21% compared to pure Na2SO4 at 800°C. The initial phase change temperature, peak temperature and latent heat of this encapsulated PCM are 885.2 °C, 887.9 °C and 170.6 J/(g. K), respectively. The TG/DSC shows that this PCM has almost no mass loss (<1 %) under calcination temperature of 1000°C. Thermophysical properties of the encapsulated Na2SO4@SiO2 varied marginally after 50 thermal cycle tests.

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