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Experiments on the Heat Storage Performance of Barium Hydroxide Phase Change Material

Beijing University of Aeronautics and Astronautics, Sheng Qiang…

    Phase change energy storage technic makes use of phase enthalpy of phase change materials storing and releasing energy in the phase change process. Among them, solid-liquid phase change materials (PCM，Phase Change Material) have advantages of isothermal or approximate isothermal phase change and high density of latent heat. They are widely applied in solar energy storage, industrial waste heat recovery, building energy efficiency, electronic thermal analysis and other fields. Hydrous salt crystal PCM is an important solid-liquid phase change materials for thermal storage under medium or low temperature. This material has advantages of high fusion heat and little volume change when melting. Compared with organic phase-change materials, it has higher heat conductivity coefficient. But hydrous salt crystal has disadvantages of serious surfusion, phase separation and corrosivity. To remove or retard condensate depression and restrain phase separation, we usually adopt the method of adding a certain amount of nucleating agent and thickening agent. At present, the way to seek given materials’ nucleating agent and thickening agent is to test and search among vast materials. Sometimes, a logical explanation for their effectiveness cannot be found. And, it takes a lot of time and effort. 
    Barium hydroxide (Ba(OH)2 • 8H20) is hydrous salt crystal which has the highest enthalpy of phase change per volume, 572 MJ/m3, at 0-120°C low phase change temperature zone discovered up to now. That is three to four times of density of latent heat of organic phase change material. Ba(0H)2 • 8H20 has consistent melting point and good freezing point with phase transformation points temperature of 78°C. Phase change materials whose melting points are within this range can be widely applied in heating, waste heat utilization, heat rejection for electronic components and other fields. But similar to most hydrous salt crystal phase change materials, Ba(OH)2 • 8H20 also has surfusion and bad nucleation property. How to control the condensate depression of hydrous salt crystal has become the focus for domestic and overseas researchers. This experiment studies different additives’ impacts on Ba(0H)2 • 8H20 nucleation property, screens out additives with appropriate dosing and practical value to improve Ba(0H)2 • 8H20 nucleation property.