Study On The Photothermal Performance Of The Vacuum Tube Type Compound Parabolic Collector With Low Interception Ratio

In the face of excessive consumption of conventional energy and deterioration of ecological environment,the modern society needs more and more environment-friendly energy,so it is in urgent need of solar collector that can replace traditional energy.Compound Parabolic Concentrator(CPC)is a concentrator designed according to the principle of light,CPC has been widely used in the field of solar heat collection.The main research work is as follows:(1)Using the solar radiation model to simplify the calculation model of the radiation received by the CPC collector,with the maximum solar radiation as the goal,the method for calculating the best inclination angles for different azimuths is given,and the solar radiation at different installation positions is theoretically derived Calculation model.Analyzed the angle relationship corresponding to CPC used in different regions of my country,and the results showed that the difference between the annual best inclination angle and the geographical latitude is no more than 5o,the best inclination angle in the winter half of the year is larger,and the best inclination angle in the summer half of the year is lower.CPC receives the most radiation when it is facing south,and the radiation begins to decrease with the increase of the azimuth,and it is more significant in high latitude areas.(2)The physical geometry model of CPC was built.The solar radiation parameters at different moments were calculated by using the program through Tracepro software.The ray tracing of CPC concentrator was completed,and the optical performance was simulated for different interception ratios and different angles.The results show that the intercept ratio from 0.50 to 0.16 can make CPC optical The efficiency is increased by more than 10%,and the determination of the optimal tilt angle can increase the optical efficiency of CPC by 2%.The energy flow density of CPC in different installation axial directions is analyzed,which is conducive to the realization of CPC’s high-efficiency concentrating and heat-collecting.(3)The accuracy of optical simulation is verified by constructing CPC light gathering and heat collecting system.The actual test of the received radiation at different inclination angles shows that the determination of the optimal inclination angle can significantly increase the received radiation.The influence of different inclination angles on the heat collection performance of CPC is studied,and the reliability of the theoretical calculation is verified.The experiment shows that the optimal inclination angle It can increase the instantaneous thermal efficiency by more than 3.9%.Explore the influence of working fluid inlet temperature,ambient temperature and effective radiation intensity on CPC’s heat collection efficiency.(4)The actual test of the thermal performance of different heat-collecting working fluids was carried out by using CPC concentrating heat collection system.At the same time,compared with traditional heat collectors,the results show that the highest outlet temperature of CPC heat collectors can be achieved when water is used as working fluid.It can reach above 70℃,and the highest heat collection efficiency can reach 0.55.The CPC air collector can obtain medium-temperature air in sunny and cloudy weather.On sunny days,the maximum outlet temperature can reach 200℃,and on cloudy days,the maximum outlet temperature is 175℃.The comparison between CPC and vacuum tube shows that the two kinds of working medium CPC has significantly higher heat collection efficiency and higher heat collection temperature than vacuum tube collector.The low intercept ratio CPC not only has good heat collection performance,but also has good economy.Through the research in this paper,the calculation model of solar radiation under different installation positions is provided,and the effective calculation method of the optimal inclination angle is given,which provides a theoretical basis for the structural optimization of CPC,and provides efficient and stable operation of CPC in the field of medium and low temperature.Certain experimental references.