Performance Study Of Loop Heat Pipe For Solar Water Heating System Of Separable Plate Type

Solar water heating system is the easiest and most common method for the use of solar energy. In this paper, the loop heat pipe technology was applied to the solar water heating system in order to achieve the purpose of long-distance and anti-gravity heat transmission. According to the design requirements, a set of flat type of loop heat pipe with ethanol as refrigerating experiment system was designed and built, and the startup characteristic, variable power characteristics and anti-gravity performance of the system were studied. The flat loop heat pipe system dynamic operation was simulated by used the Matlab/Simulink software, and the results were compared between simulation and experiment. Through the experiment and simulation, the results are as follows:(1) The startup characteristics of system was studied. The results show that: The minimum startup power of the system of is 150 W; the maximum heating power which the system will failure is 800 W, the capillary core is "dry" when heating power is higher than the maximum heating power, the system failures; the higher heating power, the shorter startup time needed.(2) The system characteristics of variable power and anti-gravity performance in open loop state was studied. The experiment found that the system to the power of mutation has good adaptive ability. When the system of heating power is lower than the minimum startup power or higher than the maximum heating power, even system is failure, the system can still return to normal through changing the heating power to the normal range. And the biggest anti-gravity of system in height is 25 mm. The reason of anti-gravity performance of system is not good enough is that the capillary pore size is not small enough, and the flow loss of working medium in the system is large. The system startup process in the condition of anti-gravity is more stable.(3) The dynamic simulation of the plate-type loop heat pipe was studied by Matlab/Simulink software, and the reliability of the model and simulation method was verified. Through the comparison with experimental results of 300 W heating power start-up process and random variable power process, the simulation results have high degree of coincidence with it. The temperature changes in the simulation results and the experimental results are basically the same, the average error of the numerical was 1.78%.(4) The state of variable power operation of the system was simulated, and the pressure loss of the working medium flow and the change of the condensing tube two-phase zone length was analyzed.The results show that the flow loss of the working medium in the circulation system is mainly focused on steam segment, and the greater the power, the greater the flow loss of working medium.So can through reforming system of steam structure to reduce the flow loss of the working medium.In addition condensation tube in two phase length increases with the heating power, can provide reference for the design and selection of the condenser type.