| It is great significance to use renewable energy for energy conservation and emissions reduction.However,due to the instability and intermittent of solar energy,storage material for solar energy is needed in order to meet the demand of energy remaining.The purpose of this paper is to prepare an optimized solar energy phase change heat storage materials,which is applied to the flat solar air collector-drying device,so as to investigate its thermal performance,and providing the foundation for improving the heat utilization efficiency of solar energy.MgSO4·7H2O,KAl?SO4?2·12H2O were selected to prepare composite with Na2SO4·10H2O individually in this thesis.A series of phase change materials were prepared,which have a low degree of supercooling and no phase separation and also have large phase change latent heat.Results show that MgSO4·7H2O-Na2SO4·10H2O mixing eutectic salt hydrate phase change materials have a good thermal stability in mass ratio 8.75:1.25,in which the phase change temperature is about 62 ?,its energy utilization efficiency can reach upto 76.37%after 200 times of hot and cold cycles.KAl?SO4?2·12H2O-Na2SO4·10H2O mixing eutectic salt hydrate phase change materials have a good thermal stability in mass ratio 9:1,and its phase change temperature is about 64?,its energy utilization efficiency can reach upto 80.87%after 200 times of hot and cold cycles.KAl?SO4?2·12H2O-Na2SO4·10H2O mixing eutectic salt hydrate phase change materials also have a good thermal stability in mass ratio 8.5:1.5,the phase change temperature is about 52 ?,its energy utilization efficiency can reach upto 75.07%after 200 times of hot and cold cycles.The salt hydrate phase change material?B4?was selected as heat storage medium in the experiment.In order to enhance the thermal conductivity,aluminum metal sheets were added in the mixed salt hydrate phase change material and aluminum fins were designed on the air side.Experimental results show that measured with the same thermal storage temperature?70??,the experimental group shortened the heat storage time about 41.2%than control group.Flat solar air collector-drying system performs a good controlling stability and accuracy,the flat solar air collector have high heat collecting efficiency upto 74.32%with in 2 hours.Besides,results of solar thermal storage experiments show that the air collector and drying oven temperature fluctuated greatly without heat storage materials,and after 1 hour it decreased to the ambient temperature.Conversely,the temperature of air collector and drying oven fluctuated small with thermal storage materials,and after 6 hours the temperature decreased to the ambient temperature,The results show that salt hydrate phase change heat storage material prepared in the experiment not only have the capacity to store solar energy and adjust indoor temperature,but also can greatly prolong the drying time and ensure the progress of the drying process. |
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