Composite Phase Change Heat Storage Technology avoids many drawbacks of sensible heat storage and phase change heat storage techniques by combining both methods. This technology has become a research hotspot in recent years, both domestically and internationally. However, traditional scaffold materials used in this technology are typically natural minerals or their secondary products. Large-scale extraction or processing of these materials can damage the local ecosystem and consume significant amounts of fossil energy. To mitigate these environmental impacts, solid waste can be used to produce composite phase change heat storage materials.
Carbide slag, an industrial solid waste generated during the production of acetylene and polyvinyl chloride, exceeds 50 million tons annually in China. The current application of carbide slag in the cement industry has reached saturation, leading to large-scale open-air accumulation, landfilling, and ocean dumping, which severely damage the local ecosystem. There is an urgent need to explore new methods for resource utilization.
To address the large-scale consumption of industrial waste carbide slag and to prepare low-carbon, low-cost composite phase change heat storage materials, researchers from Beijing University of Civil Engineering and Architecture proposed using carbide slag as the scaffold material. They employed a cold-press sintering method to prepare Na₂CO₃/carbide slag composite phase change heat storage materials, following the steps shown in the figure. Seven composite phase change material samples with different ratios (NC5-NC7) were prepared. Considering the overall deformation, surface molten salt leakage, and heat storage density, although the heat storage density of sample NC4 was the highest among the three composite materials, it showed slight deformation and leakage. Therefore, sample NC5 was determined to have the optimal mass ratio for the composite phase change heat storage material. The team subsequently analyzed the macroscopic morphology, heat storage performance, mechanical properties, microscopic morphology, cyclic stability, and component compatibility of the composite phase change heat storage material, yielding the following conclusions:
01 The compatibility between carbide slag and Na₂CO₃ is good, allowing carbide slag to replace traditional natural scaffold materials in synthesizing Na₂CO₃/carbide slag composite phase change heat storage materials. This facilitates large-scale resource recycling of carbide slag and achieves the low-carbon, low-cost preparation of composite phase change heat storage materials.
02 A composite phase change heat storage material with excellent performance can be prepared with a mass fraction of 52.5% carbide slag and 47.5% phase change material (Na₂CO₃). The material shows no deformation or leakage, with a heat storage density of up to 993 J/g in the temperature range of 100-900°C, a compressive strength of 22.02 MPa, and a thermal conductivity of 0.62 W/(m•K). After 100 heating/cooling cycles, the heat storage performance of sample NC5 remained stable.
03 The thickness of the phase change material film layer between the scaffold particles determines the interaction force between scaffold material particles and the compressive strength of the composite phase change heat storage material. The composite phase change heat storage material prepared with the optimal mass fraction of phase change material exhibits the best mechanical properties.
04 The thermal conductivity of scaffold material particles is the primary factor affecting the heat transfer performance of composite phase change heat storage materials. The infiltration and adsorption of phase change materials in the pore structure of scaffold material particles improve the thermal conductivity of scaffold material particles, thereby enhancing the heat transfer performance of the composite phase change heat storage material.
Post time: Aug-12-2024