Heat Loss Study On Solar Medium Temperature Phase Change Thermal Storage Device

Solar thermal energy application is one of the most widely ones in the prospects of new energy, one of the key factors constraining the development of solar thermal currently is the cost, how to reduce the system cost is an issue that people focus of attention. Phase change heat storage device can effectively solve the solar mismatch contradiction in time and space, is one of the key equipment in the system, but also an important part of system products. With the increase of temperature in heat storage device, thermal storage heat loss issues should not be overlooked, but people tend to be calculated in the design by the general heat transfer formula, to a certain extent, that will cause the wastage of insulation material and increasing the cost of solar thermal systems.To reduce the cost of solar thermal utilization, promotion of systems products, the paper carried out experimental analysis and numerical simulation to the solar medium temperature phase change thermal storage.First, simulation working principle of solar phase change thermal storage device, and build thermal storage experiment platform, experimental study the heat loss of heat reservoir in thermal storage and non-working condition, experimental results show that: thermal reservoir has the obvious phenomenon of phase change endothermic/exotherm in thermal storage and non-working condition. The heat loss of top surface is more serious, the heat exchanger has played a role in accelerating the heat loss.Secondly, correct the parameters on the basis of experiments, build a three-dimensional thermal analysis model, do a comparison with the experimental results, verify the accuracy of the model, by the analysis, get the heat loss coefficient K and the correction factor u, modify the theoretical calculation formula for thermal storage heat loss; analysis of the variation of temperature, liquid rate, heat flux of heat reservoir in steady and unsteady heat transfer; Get the relationship between heat loss coefficient and salt temperature, upper heat loss and heat exchangers diameter, insulation thickness. At the same time, study the influence of thermal reservoir shape, insulation materials, insulation thickness, and environmental factors as well as heat reservoir volume to heat loss, get heat loss relationship with the above factors, show that the large thermal reservoir can improve the thermal storage efficiency and reduce the system costs. Finally, on the basis of the above experimental and simulation studies, propose a new type thermal storage form-large underground heat reservoir, build mathematical and physical models, simulation analysis of temperature field and thermal storage heat loss factors The results show that:compared to thermal storage on the ground, in the winter underground heat reservoir can reduce the heat loss percentage of heat reservoir in sides and bottom to the largest19.1%. The large underground heat reservoir provides a new way of thinking for improving the efficiency of energy use, a certain reference value for the popularization and application of solar energy.