Experimental Research And Simulation Analysis Of Microchannel Solar Collector Thermal Performance

As global energy shortages and environmental pollution problems intensify,vigorously developing solar energy resources have become the focus of current energy utilization.China is rich in solar energy resources,and solar collectors are widely used in market.At the same time,microchannel heat exchangers have attracted the attention of many domestic and foreign scholars for their good heat-exchange performance.The combination of microchannel heat exchange technology and solar heat collection technology can give full play to the advantages of both technologies and that can increase the effect of energy saving and emission reduction.Therefore,this paper conducted a thermal performance study on a micro-channel solar water heater,the main work as follows:A microchannel solar water heater experimental platform has been designed and builted,which has mainly composed of four components:microchannel solar collector,circulating water pump,vortex flowmeter and hot water storage tank.The structural parameters of each component and the parameters of hardware devices such as total radiometer,anemometer,temperature sensor and pressure sensor have been introduced in detail.The uncertainty of the system has been analyzed,and the errors of the coefficient of the COP and the collector efficiency η have been within the allowable range.In accordance with a large number of experimental data,the changes of the system COP and the collector efficiency η during the three-system experiment of micro-channel collector water heater,R290 microchannel direct-expansion solar heat pump and R134a direct-expansion solar heat pump have been analyzed and compared.The average COP of the micro-channel solar water heater system is 10.82 under sunny conditions,which is 95%higher than the R290 heat pump system and 64%higher than R134a heat pump system;the collector efficiency η of the micro-channel collector hot water system is 0.71,which is 50%lower than that of the R290 heat pump system,and 53%compared to the R134a heat pump system;under cloudy conditions,the micro-channel heat collector Compared with the R290 heat pump system and the R134a heat pump system,the water heater’s heating capacity is significantly reduced;the micro-channel solar water heater circulating water flow from 0.12m3·h-1 to 0.18m3·h-1,the system COP and collector efficiency η are slightly Decrease;after adding insulation layer on the back of the collector plate,the heating capacity of the micro-channel collector water heater is obviously improved.In the experimental process of heating the water temperature to the same temperature of 51℃,the average COP is 17.92,increases of 83%,and the average heat collection efficiency was 1.16,increases of 84%.The mathematical model of the microchannel solar collector has been established and the accuracy of the model has been verified.The results show that the relative error between the experimental value and the simulated value is mostly within the allowable range of 10%,which proves that the collector model has high accuracy.The effects of solar radiation intensity,ambient temperature,wind speed and superheat on the heat collection efficiency of the collector were simulated and analyzed.The results show that the collector efficiency η decreases with the increase of solar radiation intensity and wind speed,and increases with the ambient temperature and superheat increase.Based on multiple linear regression algorithm,a micro-channel solar heat pump heat collection efficiency prediction model has established,and F test and T test are carried out on the model.The results show that the environmental parameters and operating parameters that affect the heat collection efficiency of the microchannel solar heat pump are as follows:solar radiation intensity,ambient temperature,wind speed,compressor power consumption,initial water temperature and mass flow rate.The prediction effect of the collection efficiency prediction model is good.Under the annual operating conditions,the average relative error between the predicted value and the measured value of the heat collection efficiency is 6.3%,and the maximum relative error is 17.4%,which verifies the accuracy of the model.