Study On Heat Transfer And Entropy Generation Characteristics Of The Two-Phase Closed Thermosyphon

The two-phase closed thermosyphon has been widely used because of its excellent heat transfer performance. It has simple structure and wide temperature scope. But the heat and mass transfer mechanism of thermosyphon is very complex and it’s important to investigate that for enhancing the heat transfer performance.Entropy generation analysis is a useful method for analyzing the irreversible loss of different processes. It can reveal the complex mechanism of thermosyphon including heat transfer, phase change and viscous dissipation mechanism by using entropy generation analysis method.The research of this article is forced on the heat transfer and entropy generation characteristics of the two-phase closed thermosyphon. First a numerical model and entropy generation method of thermosyphon are given. Then the entropy generation characteristics of thermosyphon during starting process is studied. At last, by analyzing different influence factors, the heat transfer and entropy generation characteristics are contrasted in different thermosyphons. All the above contents are detailed as followings:(1)A two-dimension numerical model of thermosyphon is given first, and the comparison of predicted and experimental results has proved that the numerical model is reliable. Then the entropy generation model is given to calculate entropy generation rate and entropy generation number by UDF in Fluent.(2)The entropy generation characteristics of thermosyphon during starting process is studied. It’s found that the maximum is near the wall of evaporator and the variation trend of heat transfer and phase change entropy generation are similar.They are in the majority of total entropy generation. Therefore the viscous dissipation entropy generation is ignored.(3)For different filling ratio, inner diameter, working fluid and heating power,the heat transfer and entropy generation characteristics are investigated by numerical simulation. The result shows that the thermosyphon reach top coefficient of heat transfer with 11.1 of aspect ratio, 65% of filling ratio and 200 W of heating power in this study. At last, the entropy generation characteristics under different influence factors are summarized and the result shows that heat transfer process causes much more energy quality loss than phase change process in a thermosyphon.