Study On Thermal Process Of Building Solar Collector

The efficient use of solar energy is an important means to help carbon neutrality.The main form of energy use for solar energy in buildings is still thermal energy.The collector is the core component of solar thermal utilization.And the heat pipe vacuum collector is an important application category in the solar thermal utilization market.The primary purpose of this study is to really improve the efficiency of solar heat collection by optimizing the internal structure of SCVTIHP(Solar vacuum collector tube with an inserted heat pipe)of the heat pipe vacuum collector.The main research work is as follows:1、The steady-state heat transfer mathematical model has been established by the physical model of SVCTIHP.The nanoscale heat transfer process was analyzed in combination with the microscale boundary thermal resistance.A mathematical model of the internal heat transfer resistance is established by the physical structure of the collector tube.2、A test bench for testing the thermal performance of SVCTIHP and the collector system was built.The accuracy of the description of the heat transfer process by the built model is verified by measuring the condenser end temperature and the stagnation experiment coefficient of SVCTIHP.The average error between the experimental results and the simulated value is 3.32 %,which verifies the accuracy of the single tube description of the built model.The established heat collection efficiency formula reliability was verified by the open collector and the closed water circulation system.These systems test the single-cycle heat collection efficiency of the heat collection medium and the different heat collection working fluid temperatures.And the average error of the heat collection efficiency change is 6.8 % and 2.4 %.3、The heat transfer process of SVCTIHP was quantitatively analyzed using the built model.And the structure of the collector was optimized and experimentally verified according to the main thermal resistance.The results showed:1)The thermal resistance of the main heat transfer components inside the collector tube accounts for the total internal thermal resistance as the inner glass tube for 14.4 %,the contact part of the glass tube and the fin for 4.6 %,the fin for 0.8 %,the contact part of fin and heat pipe for 22.2 %,And the heat pipe for 58 %.Combined with the improvement of the cost and effect of the heat collection tube structure,the optimization of the heat collection tube structure with the contact resistance of the fin and the heat tube as the main thermal resistance will have a better effect.2)Analyzing and predicting by the heat transfer mathematical model.The optimization of the main thermal resistance has a significant improvement in the heat transfer effect of the heat collector tube.The temperature of the condensing end of the collector tube will increase by 7.99%,and the overall heat collection efficiency of the collector system will increase by 5 %.3)The experiment uses three different thermally conductive adhesives to optimize the contact thermal resistance between the fin and the heat pipe.The average deviation between the condensation end temperature and the stagnation experiment and the predicted results are 0.14 % and 0.85 %.The theoretical model calculation results are in line with expectations.The average deviation between the collector efficiency prediction and the experimental results is 0.34 %,and the optimization results are in good agreement with the model prediction.It is further clarified that structural optimization has increased the startup speed of the collector by an average of 40.6 %.