Design And Research Of Solar Simulator Based On Radiation Heat Transfer Equivalent

With the further promotion of energy structure optimization in China,the high energy consumption of drying operation has become an urgent problem that needs to be solved in the drying field.Solar drying is an effective method to solve the energy consumption problem in drying industry.However,due to the instability of solar radiation,the experimental study on solar drying equipment and drying process is generally affected by weather.Solar simulator,as an experimental platform,can provide an ideal experimental environment for solar related experimental research.At present,most of the existing solar simulators are developed for aerospace,high temperature material testing,thermochemical reaction,photovoltaic power generation and other fields.Real solar radiation is not required to be reproduced.Therefore,most of them cannot be used for solar drying.Some of the available large-scale solar simulators are too expensive to be popularized and applied in agricultural products drying.In view of the above problems,solar simulator based on drying radiation heat transfer equivalence was designed and its performance was studied.The main work of this paper was as follows:the design requirements of the solar simulator were determined,and the solar simulator was preliminarily designed;the solar simulator light source arrangement was made by simulation experiment.Modern control methods were used in the control system of solar simulator;the performance and applicability of solar simulator were tested as well.The main conclusions were made as follows:(1)By analyzing the radiation heat transfer process and experimental characteristics in solar drying experiments,combined with the industrial standards of solar simulator,the design objectives of solar simulator were presented:the average effective irradiance is greater than 1050W/m~2,the effective radiation receiving surface area is greater than0.5m×0.5m,the direct radiation angle is adjustable from 0～30°,the uniformity of irradiance is less than 15%,the instability of irradiance is less than 5%,and the average relative error of recurring outdoor irradiance changes is less than 5%.According to the design objectives,the adjustable frame of the simulator was designed to meet the adjustable direct irradiation angle of 0～30°,and the design of the lamp array unit and the connector was completed.(2)The numerical model of solar simulator array unit was established and verified,and the numerical model of multi-lamp array was constructed,and the multi-level light array structure was optimized through the quasi-level orthogonal simulation experiment.The analysis and experimental results showed that the shape of the light array has a significant impact on the irradiance nonuniformity of the simulator,and the distance between the light sources and the height of the light array have a significant impact on the irradiance nonuniformity.The optimal light array structure was determined as a circular light array shape,the distance between light sources is 290mm,and the height of the light array is 1200mm.For the optimal structure,the irradiance nonuniformity of the effective radiation receiving surface of the simulation results is 9.7%,and the average irradiance is 1053W/m~2,which meets the design objectives.(3)The automatic control system of the simulator was designed,including the lower computer and the upper computer.The lower computer was composed of Arduino development board,DS1302 timing chip and SCR transformer module,which received the control command of the upper computer,output the corresponding PWM signal to the transformer regularly,and achieved irradiance control.The upper computer of man-machine interaction software was designed based on Labview.The experimental personnels can complete the control parameter setting through the man-machine interaction interface,and select three working modes of calibration,simulation or single value control to realize flexible control of output irradiance.(4)According to the performance test of the solar simulator,the average irradiance of the solar simulator reaches 1051W/m~2 in the effective radiation receiving surface of0.5m×0.5m,the unevenness of irradiance is 10.63%,the instability of irradiance is 1.9%,and the average relative error of recurring outdoor irradiance changes for 6 days is less than 5%.The test results showed that the simulator met the design objectives.The applicability test of air heat collector,the main collector component of solar drying equipment,was carried out.Three groups of outdoor collector experiments were carried out and reproduced in the indoor simulator environment.The average relative errors of outlet temperature of air heat collector in three groups of indoor and outdoor experiments were 0.261%,0.299%and 0.334%,respectively,indicating that the simulator has good applicability for solar drying experiments through the air heat collector.Applicability test was carried out to dry materials that were directly exposed to the sun.Three groups of applicability test were carried out for white radish,bitter melon and Chaotian pepper.According to the experimental results,the average relative errors of water ratio in the three groups of white radish drying experiments were 4.2%,7.8%and 9.8%,the average relative error of the three experiments of bitter melon was 1.5%,3.1%,4.8%,and the average relative errors of the three groups of Chaotian pepper experiments were 33%,7.8%,and 11.7%,respectively.Results showed that when the solar simulator employed in direct sunlight for drying.It has the best applicability for bitter melon,good for white radish,and average for Chaotian pepper.It was concluded that the simulator is only applicable for some certain materials.