Study On The Performance Of Concentrating Solar Air Collector

Solar energy,as an inexhaustible renewable and clean energy,has a broader application prospect than traditional energy.At present,the utilization of solar energy include solar thermal utilization and solar electric utilization.According to the outlet temperature,solar thermal utilization can be divided into low-temperature thermal utilization,medium-temperature thermal utilization and high-temperature thermal utilization.At present,the main problem faced by solar energy in the field of thermal utilization is that the thermal efficiency is greatly affected by weather,so the traditional solar heat collection devices are not ideal in the low solar radiation intensity range.In order to solve the problems of traditional solar thermal utilization,this paper combines the concentrator and solar air collector to form a new type of concentrating solar air collector.The solar light is gathered by a concentrator.At the same time,a series flow channel is used inside the device,which improves the energy retention density on the surface of the heat collector pipe and increases the time for air to flow inside the heat collector,thus further improving the heat collection effect of the device.In this paper,the geometrical structure of the concentrator is designed,and the geometrical optical performance of the concentrator is studied and analyzed by combining the relevant contents of solar geometry and the optical tracking software Tracepro.It is concluded that the direct geometric optical efficiency of the concentrator is>84%,the scattering geometric optical efficiency is>87%,and the overall optical efficiency of the concentrator needs to be analyzed according to the specific solar moment.After determining the optical efficiency of the concentrator,the heat collection efficiency and average heat loss coefficient of the collector are further studied in this paper.The results show that during the process of heat collection,the efficiency of the concentrated solar air collector is related to the inlet air flow rate and solar radiation intensity of the device,and increases linearly with the inlet air flow rate unchanged.Under operating conditions of the same radiation intensity,the efficiency of heat collection can differ by up to 18%due to the difference of flow rates.The average heat loss coefficient of the device is related to the temperature difference between the inner and outer wall of the vacuum glass tube during the operation of the device.The greater the temperature difference,the greater the average heat loss coefficient.Based on the data obtained from the experiments,a calculation model for the concentrated solar air collector is proposed in this paper,η=32.62-6.05v+0.122I+1.343v²-7.91×10^-3v I.In this paper,the influence of direct radiation ratio on the heat collection performance of the device is also studied by combining the geometrical optics content and the experimental data of the heat collection device.Since the convergence effect of the direct radiation and scattered radiation is close,the direct radiation proportion has little influence on the heat collection performance of the collector designed in this paper.Therefore,this type of collector can be used in areas with large scattering proportion.In addition to theoretical analysis and experimental data acquisition,this paper also carried out numerical simulation analysis on the heat collection unit of the concentrated solar air collector.Combining the contents of geometrical optics,the solar flow density at different times is converted into the heat flow boundary conditions related to the radial section coordinates of the collector,and the experimental conditions are well restored.The average relative error of the simulated values and experimental data is 7.0%.