Performance Research Of A W Type CPC Vacuum Collector Tubes With Heat Pipe

Compound Parabolic Concentrator is a kind of none imaging focusing condenser,the incident light that have a given incident angle can be converged to the receiver according to the ideal concentration ratio,the device can receives both direct and scatter radiation at the same time.It does not need to track sun at the time of operation continuously,it can work efficiently that only adjusted direction seasonally.In the field of solar medium temperature,the application of compound parabolic concentrator has a wide prospect.All of the research content in this paper is based on independent design,W type compound parabolic concentrator that is light internal condenser of a vacuum collector tubes with heat pipes can eliminate the leakage loss between receiving tube and reflector panel by the design.The main content is summarized as follows.(1)Firstly,the bottom and involute parabola of W type CPC are analyzed,the opening width of W type CPC reflector panel is 108.7mm,the concentration ratio is 1.236,the receiving angle is 320,the length is 1.5m.Secondly,the outer diameter of the combined heat pipe type of vacuum heat collecting tube is 28 mm and the inner diameter of the glass tube is 110mm.Lastly,the manufacturing process of CPC reflector panel,the preparation process of solar selective absorbing coating,the sealing method of glass metal and the measure of vacuum protection are introduced.(2)A model for calculating the optical efficiency of W type CPC vacuum collector tubes with heat pipes is established,the direct sunlight incident on the CPC opening surface is decomposed into radial and axial directions.The light path,geometrical optical efficiency and circumferential heat flux distribution of heat pipe are simulated by the software.The optical efficiency of the scattered radiation is calculated to be 0.487,the relationship between the optical efficiency of the direct radiation and the angle of incident and incident is studied.(3)Taking the CPC opening surface as reference plane,the coordinate system is established,the formula for calculating incident angle,radial radiation angle and axial incidence angle of the solar light and the CPC opening surface are obtained.The relationship between axial incidence angle,incident angle and direct optical efficiency is analyzed.The results show:the relationship of radial incidence angle with time is linear positive correlation,axial incidence angle changes in the range of 20°-50°,optical efficiency change less than 3%when the axial incidence angle changes in this range,The direct optical efficiency of the day was essentially stable at 68%between 10 a.m.to about 14 p.m.,and the average direct optical efficiency of the day was as high as 40%.(4)According to the basic physical parameters of solar radiation,the radiation intensity of solar radiation intensity,the intensity of reflected radiation and scattering receiving on CPC opening face are deduced,thus,the absorption intensity model of absorbing body is established.Take the day of summer solstice as an example,the total reception radiant intensity of the receiving surface is 8768.5W/m2,the average of total optical efficiency is 45%.(5)A model for energy transfer of W type CPC vacuum collector tubes with heat pipes is established,the mathematical model of the heat pipe evaporation section,the heat pipe and the condensation section is established partly.By analyzing the thermal performance of the heat collecting tube,the expressions of the instantaneous thermal efficiency equation,the total heat loss coefficient,the efficiency factor and the heat transfer factor are leading-out.The Matlab/GUI thermal performance simulation platform is designed,the results show:solar radiation intensity is the main influencing factor of thermal performance,the influence of ambient wind speed on the thermal performance of heat collecting tubes can be ignored,increasing the inlet temperature of the fluid will decrease the heat transfer capacity of the heat collecting tube,so the best fluid inlet temperature should be chosen and the inlet temperature fluctuation should be minimized as much as possible,when the fluid mass flow rate is chosen reasonably,both the instantaneous heat collection rate and the instantaneous thermal efficiency should be guaranteed,and the temperature difference between inlet and outlet can be changed obviously.