Thermal And Stress Analysis Of Absorber Tube In Parabolic Trough Collector Under Different Errors

Energy is the basics of the development of human society.With the rapid consumption of fossil fuel and the aggravation of the greenhouse effect in recent years,it’s urgent for human to find a renewable clean energy as a substitute for fossil fuel.Solar energy has been widely used as a renewable resource due to it’s abundant reserves and environmental friendliness among all the renewable energy.Currently,the parabolic trough collector（PTC）system has the highest market share among the solar thermal power generation.In present study,a PTC system was utilized to explore its’thermal performance,deformation and thermal stress performance to provide theoretical guidance for the engineering.In the actual situation,slope error(δ_sl),tracking error(δ_tr)and installation error（δ_xandδ_y）affect the PTC’s performance a lot,and two or more of them exist simutaneously.In this study,based on the optical,thermal and mechanical coupled method,the Monte Carlo ray tracing method（MCRT）was first employed to investigate the heat flux distribution on the outer surface of absorber tube under different errors,then the heat flux distribution was coupled to the finite volume method（FVM）as a volumetric heat source by UDF programming to study the temperature distribution of absorber tube,thermal efficiency and heat loss under various errors.Finally,the results of FVM were imported into the finite element method（FEM）through the Workbench platform for deformation and thermal stress analysis,whose variation with different errors were investigated.It can be sumarried as follows:The temperature distribution on the outer surface of absorber tube is similar to it’s heat flux distribution.Theδ_tr andδ_x make the heat flux and temperature distribution asymmetric.Whenδ_sl is 0mrad,increasingδ_tr andδ_x can enhance the maximum heat flux and maximum temperature of absorber tube.Increasingδ_tr andδ_xcould cause the temperature distribution more uniform and decrease the maximum heat flux and maximum temperature asδ_sl is larger.The maximum heat flux and maximum temperature gradually increase asδ_y increases from 0mm to 25mm,and the smallerδ_sl is,the faster they rise.Under the condition ofδ_tr being 6mrad,the maximum heat flux and the maximum temperature increase with the increase ofδ_x whenδ_trandδ_x has the same sign.The effects of theδ_tr and the installation error on the circumferential temperature differenceΔT of absorber tube are different under dfferentδ_sl.ΔT increases rapidly unerδ_sl of 0mrad,asδ_tr increases from 0mrad to 9mrad.The increase ofδ_tr could not causeΔT to increase asδ_sl>3mrad.ΔT increases continuously as absorber tube is moving from below the focal line to above the focal line,and the smallerδ_sl is,the fasterΔT rises.The increase ofδ_x does not cause a significant increase inΔT whenδ_sl>4mrad.The heat loss Q_loss and receiver thermal efficiencyη_r changes slightly with the scope of error considered in this study,andη_r alters fastly with the change of direct normal irradiance（DNI）.δ_x andδ_y have little effect on collector thermal efficiencyη_cwhenδ_sl andδ_trare 0mrad.Whenδ_sl>0mrad andδ_tr is 0mrad,η_cshrinks with the occurrence ofδ_x andδ_y.The optical loss reduces andη_c enhances whenδ_x andδ_tr have the same sign.δ_sl,DNI andδ_y have the greatest influence on the deflection of absorber tube.The maximum deflection of absorber tube increases significantly as the positiveδ_y augments,and the smallerδ_sl is,the faster the deflection increases.The increase ofδ_tr andδ_x does not have a great effect on the deflection of absorber tube,but could change the bending direction of absorber tube,which should be paid attention in actual engineering.In addition,the positiveδ_y can greatly increase the deflection of absorber tube,which should be controlled within a small range for safe operation.δ_tr andδ_x cause the equivalent stress distribution of absorber tuube to be asymmetric.When_sl is 0mrad,σ_equ,max rises rapidly as_tr andδ_x change from 0 mrad to9 mrad and 0 mm to 25 mm,respectively.σ_equ,maxincreases rapidly with DNI rising.σ_equ,max decreases monotonically with the increase of_tr as_sl>3mrad.σ_equ,maxis hardly affected byδ_x as_s>4mrad.σ_equ,max augments continuously as_y increases from 0 mm to15 mm.