Heat Transfer Enhancement Characteristics Investigation Of Two-phase Closed Thermosyphon

Two-phase closed thermosyphon is one of the most effective heat transfer element, its thermal conductivity higher than any other known metals. With the advantages of simple structure, low cost and excellent heat transfer performances, Two-phase closed thermosyphon has been widely used in space technology, waste heat recover, new energy development, machinery and medical field etc..The alpha magnetic spectrometer (AMS) is an international science project, which leads by Nobel physics prize winner Prof. Ting, it has been plased on international space station and first start human’s space particle experiments. Shandong University fully participated in this project from2004, responsible for the whole thermal system’s research, design, manufacture and control. Heat pipes designed by Shandong University have been applied in AMS, after3years working, it shows high heat transfer performance, which helps thermal control system becomes the most stable one of all subsystems. Based the research experiences and high TCS technology, this paper takes the thermosyphon as the starting point, focuses on the enhancement of their performances for the application of industrial and civil fields. With the purpose of strengthen the two-phase closed thermosyphon’s heat transfer performance, the paper takes experimental means as the main research methods, research and analysis the thermosyphon heat transfer characteristics under different condition and heat power input, especially the different internal structures and working fluids and double enhanced method by combining up two ways’ enhancement for the thermosyphon heat transfer characteristic. Through the research of heat transfer mechanism enhancement, this paper provides some guidance for the two-phase closed thermosyphon enhancement research.First, the research statuses of thermosyphon were reviewed. The paper introduces the heat transfer theory of the thermosyphon, analyzes the evaporator and condenser sections’ heat transfer process and coefficient of and the thermosyphon’s heat transfer limit. Take the internal helical microfin two-phase closed thermosyphon as an example, highlighted introduced its heat transfer mechanism by using high-efficiency heat transfer fluid and internal structure treatment. In the view of the characteristics of heat transfer enhancement of internal helical microfin, theoretical analysis and simulation are done for evaporation and condensation sections by using FLUENT and MATLAB, get the best highth range and heat transfer influence characterics of internal helical microfin of internal helical microfin of Two-phase closed thermosyphon.Secondly, self-designed and produced a series of two-phase closed thermosyphon, identified the thermosyphon manufacturing process and built the thermosyphon comprehensive test bench. Provide a reference for thermosyphon design, fabrication and experimental studies.Subsequently, the paper takes research in the different internal structure’s influences for thermosyphon’s heat transfer performance, particularly on the internal helical microfins along all the tube and sectional microfins along only part of the tube. Experimental results show that the internal helical microfin increased the internal heat transfer area and vaporization core, reduced the startup time of the thermosyphon. The two-phase closed thermosyphon which arranged internal helical microfin in adiabatic and condensation sections shows the best heat transfer characteristics. The continutied structure between the condensation section and adiabatic section plays an important role on the performance of thermophyson, while the continutious structural between the adiabatic section and evaporation section influences less.Finally, the paper analyzed the double enhaced Two-phase closed thermosyphon’s heat transfer characteristics which combined with internal helical microfin and self-rewetting fluid together, compared with smooth-water Two-phase closed thermosyphon and found that its’heat transfer characteristics get highly increased during the vertical and horizontal situation. The pater also analyzed the self-rewetting fliuid and water’s heat transfer performance of Two-phase closed thermosyphon. And found that during the low heating input, self-rewetting fluid gets lower working and starting temperature than water. Under the horizontal level, self-rewetting fluid’s marangoni effect has positive effection on fluid reflow, which greatly improved the heat transfer limit and strengthed the two-phase closed thermosyphon’s heat transfer performance. At the situation of vertical or high-angle level, gravity is the main driving force of reflow, marangoni effect gets weak effection on self-rewetting’s reflow. The idea by using double methods to enhance the performance eof thermoshphon provides a new way in sake for the better performance of thermophsohon in various applications.