Thermal Performance Research Of All Glass Heat-pipe Evacuated Collector

In this paper,an all-glass heat pipe evacuate heat collecting tube is designed,which replaces the metal heat pipe with a glass heat pipe.It has the advantages of easy molding,low cost and convenient market promotion.The heat pipe with glass as the shell greatly improves the heat transfer performance of the glass.The single collector and the integrated collector are taken as the research object.The whole collector is composed of multiple all-glass heat pipe vacuum heat collecting tubes and insulated water tanks.Based on the MATLAB software platform,a combination of traditional theoretical modeling and experimental research was used to establish a solar radiation intensity simulation model and a thermal model of the thermal performance of the collector.The main research contents and conclusions of this paper are as follows:(1)Based on the basic knowledge of solar energy,a calculation model and a visual calculation interface for sunny day solar radiation intensity are established.By inputting and changing local latitude,datetime and other parameters on the interface,the solar radiation intensity in any region and at any time can be obtained quickly and accurately,greatly improving the efficiency of work.The reliability of the model is verified by the measured data.The results show that the established solar radiation intensity calculation model can meet the needs of solar thermal utilization calculation.(2)For the convenience of analysis,the collector is simplified into a single collector with a single collector tube connected to the water tank,an energy analysis model is established,and the heat loss analysis of the single collector is performed according to the existing known parameters.The calculation formula is calculated by MATLAB software using the hypothetical temperature method.The thermal performance parameters,total heat loss coefficient UL,efficiency factor F’and thermal transfer factor FR of the overall collector under a certain simulation condition are obtained,and the glass is obtained respectively.The instantaneous efficiency equation is respectively used the heat pipe temperature,the fluid temperature and the fluid average temperature as a reference.(3)Taking a single collector as the research object,the effects of solar radiation intensity I,ambient temperature Ta,ambient wind speed u,fluid flow qm in the insulated water tank and fluid inlet temperature Tfi in the water tank on the thermal performance were simulated.The results show that the solar radiation intensity has a great influence on the collector.The solar radiation intensity should be fully utilized to reduce the heat loss of the collector;the ambient temperature and the ambient wind speed have little effect;the fluid mass flow rate has a greater influence on the thermal performance of the collector.Large,in the practical application should choose the appropriate mass flow to obtain the best thermal performance;fluid inlet temperature has a greater impact,and the higher the fluid inlet temperature,the smaller the fluid inlet and outlet temperature difference,the smaller the instantaneous thermal efficiency,the total heat loss The larger the coefficient,the lower the fluid inlet temperature can not be improved in practical applications,and it needs reasonable control to match the thermal performance of the collector.(4)A dynamic test platform for thermal performance of a single collector is built,and the measured data are processed and compared with the simulation results.The variation trend of the experimental and theoretical values is consistent,and the error between them is in the range of 2.38%~8.93%.A comparative experimental platform for all-glass heat pipe vacuum collector and all-glass vacuum collector is built,and the former is found to be more efficient than the latter 5%.The influence of fluid flow rate on thermal efficiency is also obtained.The thermal performance test platform of the whole collector is built,and the simulation and experimental results are compared and analyzed.The error ranges between 2.58% and 6.18% are calculated,and the causes of the error are analyzed.To some extent,the reliability and correctness of the mathematical model are verified.