The Research On Characteristics Of Heat Transfer In Evacuated Solar Collector Tube

In recent years, scholars and research institutions in domestic and abroad pay more and more attention on vacuum solar collector tube because of its good thermal insulating property. The research development and latest results from the domestic and abroad are generalized in this paper, and based on this, flow and heat transfer analysis on vacuum tube inserted within concentric stainless steel tube are presented on this paper.The mathematical model of fluid flow in vacuum solar collector, the diameter of which is 47mm, inserted within stainless steel tube is established in this paper. Based on the model, the flow field with two-dimensional symmetrical structure is established. the geometric modeling and computational basin are determined, grid division, boundary conditions, turbulence model and parameters for solving in the process of numerical simulation are completed by using the software Fluent. Flow field and temperature field distribution of the collector tube is obtained in the case of various parameters, by means of simulating flow and heat transfer inside the tube under different conditions such as different diameters of inserted tube, different flow rate, different solar radiation, etc. Through the analysis of the simulation results, law of the collector tube heat transfer performance influenced by parameters is given. According to comprehensive analysis, it is concluded that convective heat transfer in the collector tube depends on the diameter of inner tube, inlet velocity, temperature difference and solar radiation intensity.In addition, flow resistance characteristics of various diameters of inner tubes under different flow velocity condition are researched. According to the analysis and simulation results obtained, optimal performance of convective heat transfer for the collector tube requires the optimal combination of parameters. There is an optimal diameter of the feed-tube making, when the pressure flow loss is minimal. Through analysis of the vacuum tube resistance characteristics, when the feed-tube diameter is about 14mm and its flow rate is 10-12m/s, the total resistance loss is minimal.