Study On The Performance Of Large-scale Loop Heat Pipe Solar PV/T System

In order to solve the limitation of the traditional household hot water system and alleviate the hot water supply problem of residential buildings,the large-scale solar hot water system with a lighting area of more than 10 m~2 arises at the historic moment.In this paper,the large-scale loop heat pipe solar PV/T system is taken as the research object.Based on Ansys Fluent software platform,the typical working conditions and long-term operation performance of the target system are simulated.The main contents of this paper include the following aspects:(1)Using computational fluid dynamics(CFD)software,the physical model of the collector/evaporator,which is the key component of the system,is established(including the heat transfer model of the large-scale PV-LHP collector/evaporator and the mass transfer model of the collector tube).Based on the physical model,the numerical model of heat and mass transfer of the component is established on the basis of Mixture model,Lee model and standard k-εmodel.(2)The accuracy of the numerical model is verified by comparing the numerical simulation results with the experimental data measured outdoors.Secondly,in order to verify the feasibility of the system,the typical and long-term performance simulation is carried out.The temperature distribution characteristics of PV-LHP collector/evaporator and the gas-liquid phase transition law of mass transfer process of the working medium of the collector tube are simulated and analyzed.The influence of different working medium flow on the heat transfer performance of the collector tube and the collector/evaporator is discussed.The results show that the total photoelectric and thermal efficiency of the target system is 40.01%to 56.75%in the whole year,and the average annual photoelectric and thermal comprehensive efficiency is 49.06%.(3)Based on the 10 m~2 large-scale PV-LHP collector/evaporator model,the traditional 2 m~2 small-scale PV-LHP collector/evaporator model was constructed.Under the conditions of equal area and equal load,the typical working conditions and long-term performance of large-scale PV-LHP collector/evaporator and small-scale PV-LHP collector/evaporator array were compared,and the temperature field distribution characteristics of the two systems were analyzed.The results show that:the average temperature of the large-scale loop heat pipe solar PV/T system is about 10℃lower than that of the traditional collector array system,and the photothermal utilization efficiency of the large-scale system is about 3%higher than that of the traditional collector array system,and the comprehensive photothermal efficiency of the photovoltaic system is 3.68%higher than that of the traditional collector array system.On the whole,compared with the collector array system,the large-scale loop heat pipe solar PV/T system has more uniform operating temperature and better performance.