Experimental Study And Numerical Analysis Of Thermal Performance Of Mini-Channel Flat-Plate Solar Collector

With the increasing consumption of natural resources and the increasing attention to environmental problems,the development of new energy and the efficient use of traditional energy have become particularly important.Solar energy by virtue of its universal,safe,clean,harmless and other advantages,in China and the world have been widely used.As the key device of solar energy collection and transformation,the performance of solar collector directly affects the development prospect of it.However,at present,most of the optimization of solar collector is limited to laboratory measurements and not used in engineering,so the actual utilization effect is not clear.Therefore,on the basis of theory and practical application,this paper studies a new type of self-designed mini-channel flat-plate solar collector,aiming at improving the thermal performance of traditional solar collector and analyzing its practical application effect.First of on,the structure and operation mechanism of the mini-channel flat-plate solar collector are described,and the heat transfer process is defined according to the working principle and the energy balance equation.On this basis,the calculation model and evaluation parameters of the thermal performance of the mini-channel flat-plate solar collector are proposed.Secondly,in order to clarified its practical application effect,it was tested in a rural area of lvliang city,Shanxi Province in the winter of 2017.The results show that under the typical conditions of fine weather in winter,the heat collecting capacity of the mini-channel flat-plate solar collector is strong,and the average daily heat collecting efficiency is 63.6 %,and the highest is 80.4%.The average coefficient of performance of the system is 16.1.By the calculation,the average heat loss of a single heat collecting plate is 233.3W,which is concentrated at the top.At the same time,the instantaneous efficiency of the two working medium flow directions are compared,it can be concluded that the instantaneous efficiency of the flow coming from blow is higher and the heat loss is smaller.Finally,according to the experimental results and the method of numerical simulation by use of CFD software,investigating the effect of the environment parameters(solar irradiance,outdoor temperature,wind speed and others)and the operating parameters(inlet temperature,inlet flow and flow mode of cycle working medium)on the performance of the heat collector,It can be concluded that the solar irradiance and outdoor temperature have great influence on the thermal performance of the collector,while the ambient wind speed has little influence on it.It can also be concluded that reducing the inlet temperature of the working medium of the collector and appropriately increasing the inlet flow are helpful to improve the heat collecting efficiency of the collector.