Numerical Simulation Of Heat Transfer And Structural Characteristics Of Parabolic Trough Receiver With Asymmetric Corrugated Tube

Pollution-free, zero-emission and nonuse of fossil fuel are the remarkable advantages of photo-thermal utilization of solar energy. The four main typies of solar energy photo-thermal utilization are parabolic trough collectors, parabolic dish collectors, heliostats and linear Fresnel reflectors. Among the serval typies of optical collectors, parabolic trough collectors is the most commercialized type. A serious problem of the parabolic trough collector is that the thermal strain result from bend of the absorber can cause failure of the glass cover. In order to reduce the influence of thermal strain, enhance heat transfer and operational efficiency, asymmetric corrugated tube is introduced as the absorber of parabolic trough receiver in this paper.An optical-thermal-structural sequential coupled model has been developed to investigate the parabolic trough receiver with asymmetric corrugated tube. Primarily, the calculation model is established to calculate the process of solar rays concentration and transmission. Influence of structural parameter, mirror error, poingting error on the heat flux distribution of the parabolic trough receiver with asymmetric corrugated tube is investigated. Secondly, base on the study of the process of solar rays concentration and transmission in parabolic trough collector, the optical-thermal coupled model is developed combine with the user defined function. Besides, effects of the heat transfer and flow resistance characteristics influence by heat flux distribution, structural parameter and the Reynolds number are investigated. Thirdly, the central composite design method is used to get the optimal relationship of heat transfer and flow resistance base on the structural parameter and the Reynolds number. Finally, the optical-thermal-structural sequential coupled model is established for investigating the influence of structural parameter and operating parameter on structural characteristics of parabolic trough receiver with asymmetric corrugated tube.The results show that the parabolic trough receiver with asymmetric corrugated tube has a significant ability of enhancing heat transfer, besides its structural characteristics are excellent, too. Campare with the parabolic trough receiver with smooth tube, which with asymmetric corrugated tube can rise the Nussult number and the overall heat transfer performance for 65.6% and 148%, respectively, and reduce the maximum thermal strain for about 25%. Increase value of θrim and F can rise the peak value of heat flux for 37.8% and 267%, respectively. Besides, Increase value of σmirror and σpointing can reduce the peak value of heat flux for 52.3% and 75.0%, respectively. Increase p/D will both enhance the heat transfer performance and the overall heat transfer performance. It will reduce the flow resistance without loss of heat transfer ability when rise the value of rl/D. Rising value of H/D can decrease the overall heat transfer performance in the interval away from the peak value. Through heat transfer optimization, it can be known that when Nu A/Nu S is 1.92, the overall heat transfer performance reach the peak value 2.71. Value of thermal strain decrease when enhance the heat transfer ability. Both temperature distribution and structural parameters have influence on the equivalent stress. Increase value of σmirror and σpointing can reduce maximum thermal strain for 46.1% and the maximum equivalent stress for 72.3%.