Preparation and thermal storage performance study of multivalent hydrated salt composite phase change mortar for floor radiant heating

doi:10.19799/j.cnki.2095-4239.2023.0649

Abstract

Abstract:

This study focuses on the development and evaluation of a novel inorganic hydrated salt composite phase change mortar for radiant floor heating, utilizing Na₂HPO₄·12H₂O and Na₂SO₄·10H₂O as primary raw materials. The fabrication process involved the preparation of binary mixed molten salt (80%Na₂HPO₄·12H₂O-20%Na₂SO₄·10H₂O) through a physical blending method, adding a nucleating agent (2%Na₂SiO₃·9H₂O) to optimize subcooling. To enhance adsorption and encapsulation, expanded perlite particles (2—2.5 mm) were integrated, resulting in the formation of a stereotyped composite phase change material. This material was seamlessly integrated into the mortar matrix to create the composite phase change mortar. Differential scanning calorimetry tests were conducted on binary molten and binary eutectic salts, as well as stereotyped composite phase change materials, yielding enthalpies of phase change at 229.1, 214.1, and 156.7 J/g, respectively. Scanning electron microscopy revealed excellent compatibility between expanded perlite and eutectic salt phase change materials in the microstructure of the stereotyped composite phase change material. Thermal properties of the developed composite phase change mortar are as follows: 0.63 W/(m·K) thermal conductivity, 1.56 and 1.75 J/(g·K) specific heat capacity in solid and liquid states, and 3.85 W/(m²·K) heat transfer coefficient. To assess the practical impact of the composite phase change mortar, heat storage performance was tested. Comparative analysis with standard mortar demonstrated that the composite phase change mortar significantly mitigates temperature fluctuations. During the heating test with a hot plate at 50 ℃, the peak temperature of the composite phase change mortar at the cold end remained 2.5 ℃ lower than standard mortar. Additionally, the composite phase change mortar exhibited a gradual temperature rate decrease during cooling, indicating robust heat storage capabilities. When applied to intermittent radiant floor heating, the composite phase change mortar effectively stored heat during heating, preventing excessive indoor temperatures. It released heat after heating cessation, slowing down the indoor temperature reduction rate and preventing excessively low indoor temperatures. Using composite phase change mortar ensures indoor thermal comfort and minimizes indoor temperature fluctuations, implementing a heat "peak load shifting" strategy to reduce overall heating energy consumption. In conclusion, this innovative material exhibits significant potential for achieving substantial energy savings in heating systems and contributes to building energy efficiency.

Key words: inorganic hydrated salts, phase change materials, mortars, thermal storage, radiant floor heating

CLC Number:

TK 02

Jie LIU, Yingying YANG, Aizheng LI, Wensong WANG, Yan REN. Preparation and thermal storage performance study of multivalent hydrated salt composite phase change mortar for floor radiant heating[J]. Energy Storage Science and Technology, 2023, 12(12): 3655-3662.

Figures/Tables 12

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