Numerical Simulation Study Of The Factors Influencing The Performance Of Solar Trough Collectors

Solar energy is clean,renewable and abundant in China,so the study of solar energy utilization technology is of great significance.Trough collector is a kind of equipment which is more mature in solar energy utilization.It is widely used.In this paper,the factors affecting its working performance are studied.First,a thermal model of the parabolic trough sol ar collector was developed based on thermodynamic equations and actual collector parameters,and the accuracy of the model was verified by comparing and analyzing with related literature.The thermal efficiency of the collector is analyzed from the first l aw of thermodynamics followed by the fire efficiency from the perspective of the second law of thermodynamics,and the main influencing factors of both efficiencies as well as the mechanism and distribution of the fire and internal heat losses are discussed.Secondly,due to the limitations of the 1D simulation,a three-dimensional heat transfer model was established and its accuracy was verified by comparing it with the 1D simulation results by combining the concentrator simulation and the circumferential heat flow density fitting equation of the tube wall obtained from previous studies,writing the UDF program and importing it into the FLUENT software,and loading it onto the tube wall as the boundary condition.The working process of the slot collector under different operating conditions was simulated,and the temperature and velocity fields of the collector tube and its internal work mass were obtained.The analysis shows that the temperature field on the collector tube shows an inhomogeneous state,and the temperature difference is getting larger along the flow direction of the work mass.In the circumferential direction,the temperature inhomogeneity is similar to the heat flow density distribution results due to the influence of the sun irradiation and the inhomogeneous heat flow density formed by the collector itself reflection.The inlet velocity of the mass and the intensity of direct solar irradiation have a large impact on the temperature distribution of the tube wall,while the inlet working tempe rature of the mass has a relatively small impact.The largest temperature gradient of the tube wall is in the area of 80°-150° of its circumference,and the thermal stress in this area is relatively the largest.Finally,in order to improve the performance of the trough collector,a finned structure was designed on the metal collector tube.The working process of the collector tube under the new structure was simulated by FLUENT,and the temperature nephogram of the tube wall and the working medium section were obtained.And without rib before comparing the results of the analysis,found that under the new structure,on the wall of a small temperature and outlet temperature of the working medium have on the tube wall temperature gradient decreases at the same time,the temperature distribution inhomogeneity still exist,but compared with before,good uniformity,the temperature gradient in the highest position for the peripheral area of 50 ° to 140 °.After calculating the efficiency,it can be concluded that the efficiency is improved after adding the fin,and the efficiency is improved obviously at the lower inlet flow rate of the working medium.With the increase of the flow rate,the efficiency is improved less and less.The research in this paper provides a theoretical basis for the design and optimization of the collector pipe structure of the trough collector.