| Compound Parabolic Concentrator(CPC)has received a lot of attention due to its easy construction and the fact that it does not need to track the sun.Most of the time throughout the year,when the solar rays irradiate from the south side of a Standard-Compound Parabolic Concentrator(S-CPC)with circular absorber placed along the east-west direction in the northern hemisphere towards the north,not only will its southern face shape not be able to effectively concentrate light and intercept the light directly to the surface of the absorber,but also the back side of the southern side of the concentrating surface absorbs solar radiation energy after the temperature rises,thermal stress will increase,accelerating material aging,resulting in the face shape structure more easily damaged.To address the above problems,this paper adopts the principle of non-imaging optical fringe light and constructs a mathematical model of the face structure of the Shell Shaped-Compound Parabolic Concentrator(SS-CPC)based on a circular absorber,which can not only effectively eliminate the phenomenon of partial light interception by the southern face of the S-CPC,but also works normally during the daylight hours from the autumn equinox to the following spring equinox.In this paper,we have carried out the study of SS-CPC for surface shape construction and verification,optical performance,and photothermal conversion performance.1、The physical model of the SS-CPC was created using a 3D printer,and its concentrating properties were tested using a visible laser.The results revealed that:the difference between the theoretical and experimental values of the position of the incident laser reaching the absorber was no more than 1.9 mm,and the light path calculated numerically and the light path of the laser experiment was largely consistent,which verified the theoretical value;This demonstrates that the theoretically created SS-CPC surface structure is accurate.2、Seven SS-CPCs with different rotation angles(0°,15°,30°,45°,60°,75°,90°)were constructed and the optical performance was analyzed in comparison with the S-CPC with the same maximum acceptable angle,and the results of the study were as follows:the average optical efficiency of SS-CPCs increased by 13.10%,11.19%,9.36%,7.89%,5.78%,4.15%,1.80%;the relative growth rates of average geometric concentration ratio reached 7.50%,15.83%,23.33%,30.00%,37.50%,43.33%,49.17%,respectively;the annual radiation collection increased by 13.15%,19.30%,25.39%,31.15%,36.35%,40.78%,44.41%,respectively,compared with S-CPC.Throughout the year,SS-CPC has poor radiation collection performance in summer,but the solar radiation collection in spring and winter is higher than that of S-CPC,and its radiation collection characteristics form a match with heat demand in practical applications.3、The rotation angleβexhibits a positive correlation trend with the energy flux peak of the SS-CPC absorber.Whenβis 45°,the total energy received in the lower half of the absorber is 54.26%.This increases the heat transfer rate,decreases heat loss,and matches the internal temperature stratification of the heat transfer mass.The energy consumption ratio of SS-CPC withβvalue of 45°is comparable to that of S-CPC,which is 1868.43 MJ/m~2,and it has better surface curvature and energy flux distribution characteristics and more annual solar radiation collection,which has more friendly potential for engineering applications.4、The theoretical model of an SS-CPC collector system based on a vacuum tube absorber was constructed,experimental platform for solar thermal conversion of an SS-CPC collector system was built,and solar thermal conversion tests were conducted outdoors under real-world conditions.The average temperature at the vacuum tube’s exit was 72.49°C,the best solar thermal conversion efficiency was 73.89%,and the average solar thermal conversion efficiency was greater than 60%. |
