Research Of The Flux Distribution And Thermal Properties Of The Tubular Receiver In A Parabolic Trough Solar Concentrator

Solar energy has attracted more attention due to its incomparable advantage.Parabolic trough concentrated solar power generation,as one of the most mature and commercial method of solar thermal utilization still has potential to be improved,which contains the research of the properties of the solar concentrator.The flux density on the wall of the absorber of a trough solar concentrator is not uniform.The calculation of solar flux distribution is a key work to predict the temperature and the flow distribution of the fluids inner the tubular absorber.This paper presents a new method of rapid calculation of the flux distribution formed by a trough solar concentrator based on the finite element method with a sampling strategy to substantially reduce the amount of calculation and CPU time.This method can be used to work out the flux density distribution within 1 second on a level of satisfactory accuracy(standard deviation=0.1 suns).The capacity of the sampling strategy under various non-ideal conditions,such as tracking errors or alignment errors was also demonstrated.It can be applied to design optimization of trough solar concentrators and to supply boundary conditions for computational heat transfer analysis with much less computation resource than the traditional ray-tracing method.The flux distribution on the outer wall of the absorber tube distorted by non-ideal factors was calculated using the ray-tracing method and was set as the boundary condition of the model of the tubular receiver based on the finite volume method.The numerical results were compared with experimental data of the LS2 parabolic trough collector test platform and a good agreement was observed,proving that the model and method of this work is reliable.More details of the results implied the secure and stable tolerance of the receiver to non-ideal factors.It was revealed that the maximum circumferential temperature difference is 2 or 1.25 times respectively if the alignment error or tracking error exists,which are mainly cause of receivers'bending.To ensure the collecting efficiency,tracing error should be less than 0.7°.The threshold values of alignment error are 0.02m in horizontal and 0.015m in vertical.The time-dependent aperture direction can relief the harm of local overheat.