Study On Preparation Of CaCl₂·6H₂O/Expanded Perlite Composite Phase Change Material And Application In Building Energy Conservation

Due to the increasing growth rate of population and improvement of living standards,the energy consumption of buildings has increased rapidly,and research in the field of building energy conservation is necessary.Since the lightweight enclosure materials widely used in modern buildings owing to their low thermal conductivity,suffer from the insufficiency in heat storage capacity,phase change materials?PCMs?have the high heat capacity and storage capability,which can keep the same temperature and volume during their phase transitions.However,compared to the organic PCMs with inflammability and high price,the inorganic hydrate salt PCMs have high latent heat,low cost and great fire resistance.Consequently,developing a novel building envelope with inorganic hydrate salt PCMs exhibits great potential to save the building energy consumption.In this paper,expanded perlite?EP?is selected as a support material to combine with CaCl₂·6H₂O and SrCl₂?6H₂O?98:2 in mass ratio?to prepare a novel composite PCM in the practical application of buildings,whose microstructure and thermal properties are characterized by SEM?TEM?FT-IR?TG and DSC.According to physical absorption,the maximum adsorbing capacity of the phase change material in EP is 55%,and the melting temperature of the composite PCM is 27.38 ^oC,which is similar with that of CaCl₂·6H₂O.Latent heat of the composite PCM is 87.44 J/g,and thermal conductivity of the composite PCM is much lower than that of CaCl₂?6H₂O and just slightly higher than that of EP.The heating-cooling process test for 1000 cycles demonstrates good thermal reliability of the CaCl₂?6H₂O/EP composite PCM.The CaCl₂·6H₂O/EP composite PCM is fabricated into a board to replace a commercial foam board,employing as the core of insulating brick to obtain a PCM brick.The PCM brick as the roof of the test room leads to a decrease by 5 ^oC of the indoor peak temperature and a hysteresis time of about 900 s for reaching the indoor peak temperature,which indicates that the PCM brick exhibits better performance in increasing the thermal inertia and better thermal insulation property in buildings.The CaCl₂?6H₂O/EP composite PCM is fabricated into a board,embedded into an aluminous gusset plate to obtain a novel thermal energy storage aluminous gusset plate.Furthermore,a test room with the roof and the four walls equipped with the thermal energy storage aluminous gusset plates is prepared,and its thermal performance is investigated by placing it into an artificial climatic chamber.The PCM room exhibits a temperature amplitude of 16.3?C,7.6?C lower than that of the reference one without the composite boards,as well as 1.4 h longer temperature time lag.The PCM room also exhibits 34.4%in the frequency of thermal comfort,which is much higher than that of the reference one.Furthermore,the PCM room exhibits great thermal performance,showing 30%of the energy saving rate.The thermal performance of the composite PCM is simulated by Fluent and the indoor temperature fluctuation of the test room and the liquid fraction of the PCM boards is obtained,which are consistent with the experimental results with average deviation less than 2.4%.The results from numerical modeling suggest that the optimal thickness of the composite board should be around 5-7 mm.In summary,the nonflammability along with low cost,good thermal storage and insulation properties makes the CaCl₂·6H₂O/EP composite PCM show great promises for use in buildings.The as-prepared PCM brick and the CaCl₂·6H₂O/EP composite board-embedded aluminous gusset plates which show good thermal performance,are also valuable to practical applications.