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research-article

Inward Solidification Heat Transfer of Nano-Enhanced Phase Change Materials (NePCM) in a Spherical Capsule: An Experimental Study

[+] Author and Article Information
Ziqin Zhu

Institute of Thermal Science and Power Systems, School of Energy Engineering, Zhejiang University, Hangzhou 310027, People's Republic of China
11327015@zju.edu.cn

Minjie Liu

Institute of Thermal Science and Power Systems, School of Energy Engineering, Zhejiang University, Hangzhou 310027, People's Republic of China
21427105@zju.edu.cn

Nan Hu

Institute of Thermal Science and Power Systems, School of Energy Engineering, Zhejiang University, Hangzhou 310027, People's Republic of China
3140102797@zju.edu.cn

Yuan-Kai Huang

Institute of Thermal Science and Power Systems, School of Energy Engineering, Zhejiang University, Hangzhou 310027, People's Republic of China
3140103173@zju.edu.cn

Liwu Fan

Institute of Thermal Science and Power Systems, School of Energy Engineering, Zhejiang University, Hangzhou 310027, People's Republic of China; State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, People's Republic of China
liwufan@zju.edu.cn

Zitao Yu

Institute of Thermal Science and Power Systems, School of Energy Engineering, Zhejiang University, Hangzhou 310027, People's Republic of China
yuzitao@zju.edu.cn

Jian Ge

Institute of Building Technology, School of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058, People's Republic of China
gejian1@zju.edu.cn

1Corresponding author.

ASME doi:10.1115/1.4037776 History: Received January 10, 2017; Revised July 17, 2017

Abstract

The classical problem of inward solidification heat transfer inside a spherical capsule, with an application to thermal energy storage, was revisited in the presence of nano-enhanced phase change materials (NePCM). The model NePCM samples were prepared by dispersing graphite nanoplatelets (GNPs) into 1-tetradecanol (C14H30O) at loadings up to 3.0 wt.%. The transient phase change, energy retrieval, and heat transfer rates during solidification of the various NePCM samples were measured quantitatively using a volume-shrinkage-based indirect method. The data reduction and analysis were carried out under single-component, homogeneous assumption of the NePCM samples without considering the microscale transport phenomena of GNPs. It was shown that the total solidification time becomes monotonously shorter with increasing the loading of GNPs, in accordance with the increased effective thermal conductivity. The maximum relative acceleration of solidification was found to be more than 50% for the most concentrated sample, which seems to be appreciable for practical applications. In addition to enhanced heat conduction, the possible effects due to elimination of supercooling and viscosity growth were elucidated. The heat retrieval rate was also shown to be increased monotonously with raising the loading of GNPs, although the heat storage capacity is sacrificed. Despite the remarkable acceleration of the solidification time, the use of a high loading (e.g., 3.0 wt.%) was demonstrated to be possibly uneconomical because of the marginal gain in heat retrieval rate. Finally, correlations for the transient variations of the melt fraction and surface-averaged Nusselt number were proposed.

Copyright (c) 2017 by ASME
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