| The increasing demand for energy by humans and the environmental problems brought about by the large consumption of fossil energy,the development and use of renewable energy resources have become particularly important.Solar energy is a promising new energy source.It is a clean energy source that can be seen everywhere.However,solar radiation is very unstable due to the effects of day-night alternation and weather,so it is necessary to use thermal storage technology or heat storage materials to store solar energy so as to achieve continuous supply of thermal energy.This article reports the preparation and performance test results of phase change thermal storage composite MgSO4·7H2O/KAl（SO4）2·12H2O,including the phase transition temperature,the latent heat of phase change,the stability of the heat release performance,and the phase change heat storage composite material was combined with a flat-plate solar air-heating-drying device,and the results of heat collection performance analysis and drying performance test were performed.The realization of the thermal storage and utilization of solar energy provides the basis for improving the solar thermal utilization efficiency.A series of MgSO4·7H2O/KAl（SO4）2·12H2O solar phase change thermal storage composites with low degree of undercooling,no phase delamination,and large latent heat of phase change were prepared by mixed eutectic method.The phase transition temperature of the phase-change thermal storage composite with MgSO4·7H2O/KAl（SO4）2·12H2O mass ratio of5:5 is 43.7℃,the melting temperature is 47.8℃,There is no phase delamination and the degree of supercooling is 4.1℃.During the exothermic process,the exothermic platform lasts for a long time and its performance is stable.After 350 times of melting-solidification cycles,the phase change heat storage composite material has a heat release rate of 75.35%.It is a very promising low-temperature solar phase.change heat storage material.In the container to set the thermal conductivity of aluminum,the outer container to set the fin way to enhance heat transfer,a good solution to the storage and storage heat mixed hydration salt poor thermal conductivity and air side of the large thermal resistance issues.The experimental results show that phase change material with MgSO4·7H2O and KAl（SO4）2·12H2O ratio of 5:5 is the heat storage medium,which is measured at the same temperature（70℃）at the most central position in the material.The thermal storage time of the heater A is shorter than that of the thermal storage B by about 37.50%.Experiments in solar drying applications show that after shading of the collectors,the temperature in the collectors and drying ovens of the non-thermal storage materials group varies greatly,and the average temperature drop in one hour after shading is 57.19%and32.96%,However,the temperature drop in the collectors and drying ovens of the regenerative materials group was relatively slow,with an average temperature drop of 20.79%and 16.36%,and after about three and a half hours and two and a half hours of collectors and drying.The device temperature will drop to 57%and 33%without phase change material.With the solar collector-dryer with regenerative material and the natural drying,the moisture of the sample was lost,and the rate of water loss of the sample in the solar drying device was significantly higher than in the case of natural drying.It shows that the phase change heat storage material plays a certain role in temperature regulation,and it greatly extends the drying time. |
PDF Full Text Request