A Theoretical Study Of A Gravity- Assisted Loop Heat Pipe Solar Collector

Considering the recent development and tendency of the solar thermal utilization and the undergoing research program in our institute, a new idea was suggested that a loop heat pipe was integrated into flat plate solar collectors with aiming at developing a new solar water collector. In this study, a mathematical procedure was suggested for simulating its thermal performance based on a typical climatic condition of Kunming.The direction of solar thermal utilization is towards the building integration of solar energy systems, and the solar flat plate collectors is one of the best types of collectors for such combination.Yunnan province is the biggest market of solar flat plate collectors in China. But the poor anti-freezing is resisting its rapid spread in other areas of China.The key of the solar thermal utilization is the development of high quality solar collectors. Due to heat pipes can be formed various shape to meet technical requirements of a collector, so it is easily integrated with solar collectors.The heat pipe, being not fully filled, has some free space for expansion of working fluids when it freezes. Compared with the commonly used flat plate solar collectors, such collectors have good performance for anti-freezing.Due to the perfect heat transfer of a heat pipe, it has been widely used in many areas such as aviation, chemical industry and solar energy. Because the heat transfer of two phase closed thermosyphonic heat pipes is one-way, thus these collectors can effectively prevent reversed circulation of working fluid at the night.In this study, a new solar collector system was designed by integrating a loop heat pipe into a solar collector, a mathematical model was suggested for the theoretical investigation of its thermal performance, and the effects ofsome structural parameters on its thermal performance was studied by simulations.The simulating results indicated that this new system performs better than commonly used flat plate collector does if thermal resistance of the condenser inside a cooling water tank is not taken into consideration. The resistance of evaporator, which is mainly dependant on the efficiency of fin, is very little. The results also indicated that the most important for a thermally better collector is to improve heat exchange of the condenser.