Development Of Low Temperature Phase Change Energy Storage Materials And Research On Phase Change Hysteresis Performance

Phase change energy storage is a new type of energy storage technology that can improve energy utilization and achieve high efficiency and energy saving.Phase change materials mainly realize the efficient storage,conversion and utilization of energy in the form of latent heat.It is widely used in the fields of solar thermal utilization,cold chain logistics,building energy conservation,waste heat recovery,and electronic equipment industry.At present,the research on phase change energy storage technology at home and abroad has gradually become a hot spot,but most studies on the phase change process are lacking,that is,the phase change hysteresis characteristics are not considered.The phase change hysteresis has a significant effect on the phase change heat storage and release process.The hysteresis characteristics of phase change materials can be used to realize the intelligent adjustment of the phase change temperature.It is widely used in the military field and can be used to reduce the target heat radiation camouflage,Field refrigerated vehicle coating,warm board house coating and warm sleeping bag clothing,etc.This paper mainly studies the influencing factors of phase change hysteresis characteristics,provides theoretical basis for realizing the parameterized control of phase change hysteresis characteristics,and plays an important role in promoting the development of phase change energy storage technology.This article mainly does the following work: Prepare a low-temperature eutectic composite phase change material,and use the composite phase change material as the research object to study the phase change hysteresis characteristics.Based on the wide range of applications of low-temperature eutectic phase change materials,they are mainly used in construction,solar water heating systems,textiles and other fields,and are closely related to human production and life.Therefore,it is proposed to develop a lowtemperature eutectic hydrated salt phase change that meets the needs of production and life.material.A low-temperature eutectic material CaCl2·6H2O-MgCl2·6H2O was prepared,in which the mass fraction of MgCl2·6H2O was 10%.On the basis of the eutectic material,2% strontium chloride hexahydrate was added as a nucleating agent,0.3% As a thickener,hydroxyethyl cellulose effectively reduces the supercooling of the composite phase change material and inhibits phase separation.The phase change temperature of the new composite phase change material is 27.9°C,the latent heat of phase change is 172.8 k J/kg,and the subcooling degree is 0.4°C.After 50 cycles,the latent heat value of phase change drops by 0.4%,and the thermal performance is stable,meeting low temperature requirements.Needs in the field of production and life.Combining the mechanism of the phase change hysteresis characteristics,experiments are conducted to study the effects of heat storage temperature,cooling temperature,cooling rate,nucleating agent content,thickener content,ultrasonic wave and other factors on the phase change hysteresis.The developed new composite phase change material CaCl2·6H2OMgCl2·6H2O-2% SrCl2·6H2O-0.3% HEC was used as the experimental object,and the heat storage temperature,cooling temperature,cooling rate and other factors were changed to conduct heat storage and release experiments.Combined with the T-history research method,the temperature acquisition instrument was used to draw the step cooling curve;the differential scanning calorimeter was used to measure the DSC curve,and the results obtained by the two test methods were completely consistent.It is found that under the condition of ensuring the complete phase change of the phase change energy storage material,the higher the heat storage temperature,the lower the phase change hysteresis;the lower the final cooling temperature,the greater the phase change hysteresis;the lower the cooling rate,the lower the phase change hysteresis The higher the degree.The greater the mass fraction of the nucleating agent,the greater the degree of phase transition hysteresis;the greater the mass fraction of thickener,the greater the degree of phase transition hysteresis.As the amplitude of ultrasonic vibration decreases,the hysteresis of the energy storage material first decreases and then increases.Finally,use COMSOL simulation software to study the phase change hysteresis characteristics under different pressure conditions.It is found that as the pressure increases,the phase change hysteresis degree becomes larger.The research on the low-temperature eutectic phase change energy storage materials and their phase change hysteresis characteristics developed in this paper enriches the heat storage and release theory of phase change materials,provides new ideas for optimizing the performance of phase change energy storage materials,and provides a new way to achieve phase change Parameterized control of lagging influence factors provides the possibility.