Effect Of Thickeners And Nucleating Agents On Properties Of Mirabilite Based Phase Change Energy Storage Materials At Different Temperatures

Mirabilite based phase change materials(PCMs)have superior performances on nearly isothermal process,wide phase transition temperature range,and higher thermal storage densities.Mirabilite based PCMs use solid-liquid phase reversible change to realize energy recycling and increase energy efficiency.Not only is the cost low,but the environmental protection is also green.In the era of resource shortage,the PCMs have high application value and broad market space.In this paper,the effects of several kinds of thickening agent and nucleating agent on the properties of three phase change materials with different phase change temperature are investigated.Finally,the instant and high viscosity carboxymethyl cellulose sodium(CMC-Na),the instant and high viscosity xanthan gum(XG)and self-made pulp fibers are selected as thickening agent respectively.Boric acid,borax,water quenched silicon carbide at 1100 ? as nucleating agent respectively.By means of Fourier transform infrared spectroscopy(FTIR),differential scanning calorimetry(DSC)and scanning electron microscope(SEM),the effects of the optimum type of viscous agent and the addition amount on the energy storage density,thermal conductivity and undercooling of three kinds of temperature gradient phase change materials were investigated.The results show that the ratio of instant solution and high viscosity CMC-Na in 3 kinds of PCMs with different temperature gradient is 1.0%,1.0% and 0.5%,respectively,and the temperature of phase transition is 7 ?,respectively.At 14 ? and 22 ?,500 cycles of freezing and thawing are not stratified.At 22 ?,14 ? and 7 ? PCMs,the content of instant solution and high viscosity XG was 1.4%,2.4% and 1.0% respectively,and the fiber addition amount of self-made pulp was 1.2% 1.4% and 1.0%,respectively.The phase separation can be prevented,and its storage energy density,thermal conductivity and undercooling degree can greatly improve the thermal storage property of the phase change material and prolong the service life of the phase change material.Borax,boric acid and water-quenched silicon carbide at 1100 ? were selected as nucleating agents.At the same time,the 22 ? phase change energy storage material was used in the agricultural greenhouse.The effect of modified 22 ? nitrate-based PCMs on nighttime temperature rise in greenhouse in demonstration area is obvious.In clear day,sunny turning to cloudy day,cloudy weather,overcast,the night temperature can be raised by 7.5 ?,4.8 ?,2.8 ? or 1.7 ? respectively.The application of modified 22 ? phase change material can effectively improve the thermal environment of greenhouse in winter of Tibetan Plateau and accelerate the growth of crops.Three kinds of temperature gradient glauberite based PCMs can be used in accordance with practical application,which can greatly meet the needs of application.At the same time can be recycled,play a long-term mechanism,green environmental protection.