Numerical Simulation Of Thermal Performance Of A Hybrid System Of Solar Heating And Radiative Cooling

The thermal utilization fields of solar energy is extensive.Flat plate solar collector is gaining more and more attentions due to its good pressure bearing capacity and high extent of integration with building.But the initial investment costs are high and the collectors remain sidle at nighttime.In this paper,finite element analysis software is applied to analyze a combined system(Solar Heating-Radiative Cooling,SHRC)that has complementary functions of solar heat collection at daytime and radiation refrigeration at nighttime.The influence of different factors,such as radiation intensity,inlet temperature etc.,on the performance of SHRC are explored in this paper.Performance relations under two conditions of heat collection at daytime and radiation refrigeration at nighttime are obtained.The main contents and conclusions are as follows:1.Mathematical model of SHRC combined system based on normalized temperature is established.The influence of different factors on the thermal performance is studied by using Fluent.The model is proved by experiment data.The thermal efficiency of the experimental results and the numerical solution at zero-reduced temperature is 63.6%and 60.3%respectively,and the root mean square deviation(RMSD)is 2.84%.For example,the thermal performance of Hefei in different seasons is calculated.The results indicate that the reliability of the system performance is the highest in summer.2.By using finite element analysis software(Fluent),the refrigeration capability of SHRC are investigated.The relationship of refrigerating capacity with(Tin-Ta)is obtained and compared with the experimental results.The simulation results is higher,and RMSD between the experimental and simulation results is 13.85%.The theoretical cooling capacity at zero-reduced temperature is satisfied approximately 45%of the demand of a typical unit room at summer night.Within a certain range,the above relationship equation can be used to predict and analyze the relative change of SHRC refrigeration performance.3.Based on the typical weather year data,the effects of different parameters on the thermal performance of the hybrid system in six cities in conditions with different climate variations are investigated.The results show that the thermal properties of SHRC are related to the climate types and seasons of the region owing to the different irradiation conditions and ambient temperature.The different types of climate systems change with heat storage capacity.Except for the typical tropical rainforest climate in Singapore,year-round heating and cooling capacity are more evenly distributed in these six cities.Others vary with the seasons,with the largest amount of the annual heat and the least,respectively,Canberra and New York.The difference between the capacities of two cities is 1257.39 MJ/m~2.In addition,some practical suggestions are put forward in this paper to improve work efficiency in individual areas or seasons with insufficient performance.