| At present,the energy crisis and environmental pollution is increasingly serious,therefore,exploring the efficient usage of the wind energy,solar energy and other renewable energy is essential.The study builds a double-axis tracking trough solar concentrator system to study the characteristics of the concentrating and the collecting of system on the basis of previous research.Firstly,design the new test target,test the focus spot temperature field,and measure the focal spot width under different positions.And adopt a method to calculate the focal center offset.The results showed that when the direct irradiance of the sun is 864.1W/m2,the maximum temperature of the focal spot reach up to 220.1 ?.When the direct irradiance value change from 809.8 W/m2 to 860.1 W/m2,the uniformity of the focal spot temperature distribution decreases rapidly.The change range of focal spot width for every test position is from 45 mm to 108 mm.Take advantage of the Gaussian function fitting method to get the center shift value of the corresponding focal spot is 2.68 mm,1.89 mm,-0.20 mm,2.76 mm and 9.83 mm respectively.Secondly,used the energy density sensor to measure the flow density distribution of the focal spot under the clean mirror and the fouling mirror respectively,and calculate the change trend of acquisition factor under different aperture of heat absorber.The results showed that the maximum energy density of focal spot is 8.6% lower than that of the clean mirror when the relative reflectivity of the condenser is reduced by 1.3%.The fouling is favorable for the heat sink to receive more energy under the experimental conditions.Thirdly,the study adopting optical simulation software to analyze the energy density distribution of vacuum tube heat absorber at different receiving positions,and using CFD software to determine the test range of experiments.The optimal receiving position is experimentally tested,and the mathematical model of the thermal efficiency prediction is determined by the dimensional analysis method.The results showed that the optimal receiving position is from 445 mm to 465 mm under different flow conditions,and the mathematical model of collector efficiency is obtained by SPSS software.The multiple regression method is ?=1.514·Re-0.291·C10.08·C2-0.252·C3-1.946·C 4-0.26.Finally,adopt the dynamic test method to analyze the change of instantaneous heat collection efficiency of system and normalize it.The results showed that the instantaneous heat collection efficiency decreases with the increase of flow rate,and the deviation gradually decreases with the increases of time.The maximum heat collecting efficiency under the three flow conditions is 83.33%,69.37%,81.78%,and the thermal loss coefficients is 14.44W/?m2K?,12.49 W/?m2K?,10.76 W/?m2K?.The thermal loss coefficient is obtained as a function of the flow change through function fitting,so as to provide data support for the subsequent heat utilization. |
PDF Full Text Request