Characteristic Study On Improved Thermosyphon Loop

Thermosyphon loop has some advantages, including no capillary structure to be used, simple structure, easy to manufacture, etc. It still has attractive features that it relies on gravity to cycle, the vapor and liquid have their own channel, the thermal resistance of the evaporating and condensing section is small, and heat transfer is achieved by the phase change. Therefore it is a very effective way to solve the electronic device cooling.How do the thermosyphon loop’s boiling limit and heat exchanger performance be improved? In this work, from the refrigerant side, some measures are taken, such as improving the working fluid disturbances, speeding up the bubbles departure, etc. Based on these, an advanced thermosyphon loop using bubble pump effect is proposed, and the experimental apparatus is built in order to enhance the heat transfer of evaporating end and improve the heat and mass transfer of thermosyphon loop by the chip’s waste heat drive.In addition, to further strengthen the evaporation chamber boiling heat transfer, an evaporator ultrasonic devices is introduced to greatly increase the secondary gasification core, according to the spray cooling heat transfer mechanism. The whole contents in this work are as follows.(1) The thermosyphon loop operation mechanism is outlined, the basic theory and models on enhancing the boiling heat transfer of of thermosyphon loop are analyzed, and the program to strengthen the heat transfer of evaporating section is proposed.(2) An advanced thermosyphon loop using bubble pump effect is proposed a) The relevant components of experimental apparatus (including the evaporator, condenser section, reservoir, heating parts, measuring part) are designed, working fluid is selected, heating and evaporating section is made, the heating program is selected, temperature the distribution uniform in the heating section is considered, etc. The experimental program is figured out.b) Effect of the condensing temperature, heating power and other parameters on the total thermal resistance and the surface temperature of heat source.The variation of the total thermal resistance, surface temperature of heat source with of the condensing temperature a, heating power and power flux etc, are obtained by experimental study, effect of charging height of the working fluid on the heat transfer of thermosyphon loop is analyzed. Meanwhile, the experimental results show that the using of bubble pump effect will increase the heat transmission resistance and effectively enhance the demonized water turbulence in evaporator cavity, which leads to increase of heat transfer capacity and critical heat transfer heat flux. When the heat load is646W, the minimum thermal resistance is0.11℃/W. In addition, there exists an optimal charging liquid level. From the analyses of the flow patterns, it can be known that the charging height is reasonable when the flow pattern is annular flow in the ascending tube. The evaporation thermal resistance is still one of main barriers to further reduce the overall thermal resistances.(3) The evaporation chamber ultrasonic atomizer’s effect on the total thermal resistance and the surface temperature of heat sourceThe heat dissipation performance of gravity assisted loop heat pipe is analyzed after the ultrasonic atomization device is installed in the previous experimental appartus.Deionized water is atomized into droplets by ultrasonic atomization device, which rise by means of buoyancy and touch with the wall. The preliminary experimental results show that to a certain extent, the atomized droplets can improve the boiling heat transfer coefficient.Therefore, in this work, it is thought that boiling heat transfer within the film (boiling bubbles include the surface nucleation bubbles and secondary nucleation bubbles) plays an important role in enhancing the heat transfer in the atomization method. All above research will provide a valuable reference for the field of chip cooling.