Optimization Of Solar Heating System With Phase Change Heat Storage In Cold Regions

In recent years,with the continuous progress and development of social economy,energy depletion and energy waste have attracted more and more people’s attention.Many harmful substances are produced by traditional energy,which lead to serious ecological and environmental problems,such as global warming,acid rain,haze and so on.It has broad prospects to promote and develop renewable energy represented by solar energy.From the perspective of building energy conservation,applying solar energy to the heating system of rural residential buildings in cold areas can reduce the use of traditional energy and improve the indoor environment quality.In this thesis,the typical individual rural building in cold region is taken as the research object.Its solar heating system with phase change heat storage has been optimized.The main contents and conclusions of this research are as follows:(1)Under the conditions of meteorological parameters in a typical year in Jinzhou area,the dynamic heat load of typical individual building in rural areas has been simulated.The construction area is 113m~2,and the heating area is 87m~2.In order to reduce the heat loss in winter,insulation materials are used on the external wall.In the solar heating system with phase change heat storage,the selection calculations of collector,auxiliary heat source,heat storage tank,water pump and other equipment have been carried out.(2)The phase change water tank structure suitable for the heating system has been designed.The heat transfer model of phase change water tank has been established by Fluent,in order to simulate and optimize its performance.For phase change material comparsion,the heat storage and release processes of paraffin and myristic acid have been simulated.By changing the inlet temperature and velocity of the phase change water tank,the temperature and heat storage changes of the phase change material in the process of heat storage and release has been compared.The simulation results show that:the endothermic process of paraffin is shorter than that of myristic acid,while the exothermic process of myristic acid is longer than that of paraffin;the larger the flow rate,the faster the temperature of phase change materialchanges;the slower the flow rate,the slower the temperature of phase change material changes;the higher the inlet temperature of phase change water tank,the faster the temperature of phase change materialchanges,and the shorter the phase change timeoccurs;the higher the inlet temperature is,the faster the phase change material temperature changes,and the shorter the phase change time is in the exothermic process.Paraffin was selected as the phase change material and the inlet flow rate was 1m/s.(3)Based on Trnsys software,a solar heating system with phase change heat storage was built.Combining with the annual cost method,the objective function was established to optimizationwith the variables of the solar collector angle,azimuth,collector area,phase change water tank volume and phase change material thickness.Using Genopt software to call Hooke Jeeves optimization algorithm,the results of the synchronous optimization of various variables of the solar heating system show that the best inclination angle of the solar collector is 51°,the best azimuth Angle is 7°south by west,the area of the solar collector is 21.25m~2,the volume of the water tank is 1.25m~3,and the thickness of the phase change material is0.063m.The annual cost is 6869 yuan,and the annual cost is reduced by 1076 yuan.In this thesis,through the optimization research of solar heating system with phase change heat storage in cold areas,the parameters and optimization methods to improve the economy of solar heating system are proposed.These methods provide theoretical support for the design and application of solar heating system in rural single building,and is helpful to promoting the application of clean energy in the heating system for rural residential building.