Energy Storage Science and Technology ›› 2021, Vol. 10 ›› Issue (5): 1720-1728.doi: 10.19799/j.cnki.2095-4239.2021.0319

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The preparation and thermophysical properties of chloride/ceramic-shaped stabilized composite phase-change materials

Wenbing SONG(), Yuanwei LU(), Xiaotong CHEN, Cong HE, Zhansheng FAN, Yuting WU   

  1. Key Laboratory of Enhanced Heat Transfer and Energy Conservation of Ministry of Education and Key Laboratory of Heat Transfer, Beijing University of Technology, Beijing 100124, China
  • Received:2021-07-05 Revised:2021-07-15 Online:2021-09-05 Published:2021-09-08

Abstract:

This study aimed to develop a type of low-cost heat-storage material with good thermal performance. Chloride salt (CaCl2-NaCl-KCl) was selected as the phase-change material, alumina (α-Al2O3) was used as the matrix material, and expanded graphite (EG) was used as a thermal conductivity enhancer. A mixed sintering method prepared the CaCl2-NaCl-KCl/α-Al2O3/EG stable composite material. Based on X-ray diffraction results, chloride, alumina, and the EG physically mixed, but no chemical reaction occurred. Scanning electron microscopy was used to observe the microstructure of the EG. Chloride and alumina were evenly mixed and adhered to the pores of the EG. The pores formed by the EG helped to prevent liquid leakage. The results showed that the melting point of the composite was almost the same as that of chloride. By measuring the thermal properties of the composite material, the results showed that the specific heat capacity of the CaCl2-NaCl-KCl/α-Al2O3/EG composite material was 1.35 J/(g·K) before the phase change (150~450 ℃), and the thermal conductivity was 5.03 W/(m·K). After the phase change (520~640 ℃), the specific heat capacity was 1.43 J/(g·K), and the thermal conductivity was 5.03 W/(m·K). Compared with the chloride salt, the melting point of the composite material essentially remained unchanged. In the application range of 100~700 ℃, the composite material's heat storage per unit mass was 902.5 J/g, increasing 8.3% compared with the pure chloride salt. In the prepared CaCl2-NaCl-KCl/α-Al2O3/EG composite material, the chloride salt avoided direct contact with the container during use, thereby reducing its corrosiveness. Concurrently, the thermal performance greatly improved. This study provides an alternative low-cost and good comprehensive performance heat-storage material for high-temperature heat-storage contexts. It provides an experimental basis for promoting the practical application of chloride in high-temperature heat-storage environments.

Key words: chloride, alumina, expanded graphite, composites, thermophysical properties

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