Numerical Simulation Of Heat Transfer Performance Of Solar Receiver Absorber With Non-uniform Heat Flux

Energy plays an important role in the development of national economy.At present,the serious environmental pollution caused by the use of fossil fuels,which is the main energy type,has affected the development of human beings.Among the clean energy technology,solar thermal power generation technology has been widely concerned by researchers and government departments because of its low-cost prospect and inherent advantages of matching with high-temperature heat storage technology.Solar power tower station is developing rapidly because of its high concentration ratio,high capacity and high efficiency.However,compared with traditional thermal power plants and hydropower plants,the cost of power generation is still too high,so it is difficult to carry out large-scale commercial promotion.As the core component and the biggest exergy loss component of the solar island in the solar power tower station,the improvement of its efficiency and stability is very significant for the whole power station system.In this paper,the cavity tubular receiver,which is widely used at present,is taken as the research object,and the binary molten salt solar salt is the heat absorbing medium.The physical model of single heat pipe is established by ICEM software,and the simulation is carried out by FLUENT software in which the boundary conditions are set up based on HFCAL heat flux model.By comparing the results of the calculation of the circular tube and the transverse tube,it is found that the axial vortex of the molten salt is formed on the tube wall due to the effect of the convex ribs of the transverse tube,which increases the disturbance of the boundary layer,reduces the thickness of the boundary layer and enhances the heat transfer.And the temperature difference of the cross section at the outlet is smaller than that of the circular tube,which can effectively improve the stability and service life of the absorber.In order to optimize the size of the transverse tube,an efficient experimental scheme was designed under the guidance of the orthogonal experimental design method.According to the test results,the prediction of the optimum tube structure is put forward,and the correctness of the prediction is verified by simulation.The comprehensive factor of enhanced heat transfer of the new tube type is 1.631,which is higher than that of 25 groups of tube types in all orthogonal tests,and the circumferential distribution of temperature of molten salt in the tube is more uniform,so that its stability and service life are further improved.Finally,the concept of field synergy number Fc and dimensionless factor Φ is introduced,and the mechanism of heat transfer enhancement of the transverse tube is analyzed systematically by using the Field Synergy Principle.Through the comparative analysis,it is found that the conclusion of the comprehensive performence of the transverse tube in heat transfer enhancement based on the field synergy principle is consistent with that under the traditional criterion η.It is proved that the performance factor Φ is correct as the comprehensive performance evaluation criterion of enhanced heat transfer,and the field synergy principle is more systematic and scientific in the analysis of enhanced heat transfer.