Research On Improving Thermal Efficiency Of Solar Vacuum Collector Tube With Inserted Runner

In recent years,the solar vacuum tube collector has been widely concerned by many scholars and research institutions at home and abroad for its good heat collection and insulation characteristics.It is an energy-saving and environmental protection application product with the most mature technology and the most investment value in the development of solar photothermal conversion application.Most of the vacuum collector tubes in the common solar collectors in the market are made of copper tube and aluminum tube,but their prices are high,and there is little research on the vacuum collector tubes of other tubes.Based on this problem,this paper proposes to use PPR tube instead of copper tube and aluminum tube in the vacuum collector tube.Firstly,the structure and working principle of the solar vacuum tube collector are discussed,the type of vacuum tube collector suitable for this study is selected and the diameter size of the vacuum tube collector is determined,and then the solar radiation energy and the thermal performance of the vacuum tube collector are simply analyzed.In this paper,a mathematical model of solar vacuum collector tube with outer glass tube diameter of 58 mm,inner glass tube diameter of 47 mm,wall thickness of 1.6mm and tube length of 2m is established,which provides a theoretical basis for studying the thermal performance of the collector tube.The geometric modeling,Calculation Basin Determination,grid division,Boundary Condition Selection,turbulence model selection and solution parameter setting in the numerical simulation process are carried out by using Fluent software,based on the numerical simulation of the flow and heat transfer in the collector tube with different diameter and inlet velocity,the flow field and temperature field distribution in the collector tube with different parameters are obtained,the influence of each parameter on the convective heat transfer performance in the collector tube is obtained.At the same time,the resistance characteristics of vacuum collector tubes under different diameters and different flow rates were studied,and the heat collection efficiency of vacuum collector tubes under different parameters was analyzed.According to the analysis of simulation results,it can be concluded that for a single vacuum collector tube,when the PPR tube with diameter of 25 mm is arranged eccentrically by 6mm and the inlet flow rate is 0.5m/s,the heat transfer effect of the collector tube is the best,and the average daily heat collection efficiency can reach 59.3%.By comparing the energy cost and benefit of different hot water boilers,the best economic benefit of using electric heating as auxiliary energy in solar water heating is obtained,and the energy saving benefit and social benefit of the system are analyzed.Through the minimum annual fee method and life cycle cost method,the economic analysis of solar heat collection system and coal-fired boiler hot water system shows that the saving rate of solar heat collection system is about 70% compared with the coal-fired boiler hot water system,and the static investment payback period of solar heat collection system is about 4.9 years.