| Environment pollution and energy supply has been severe stressed, so it is extremely urgent for energy conservation and emissions reduction. Heat pipes, with its excellent heat transfer performance and technical characteristics, have been applied in the thermal control system of spacecraft all the time. As an efficient heat transfer component, it is becoming more and more popular in the application of engineering, such as new energy development, motive power, chemical, textile, production, especially waste heat recovery and energy saving.The alpha magnetic spectrometer02(AMS-02) is an international cooperation project, which aims to explore the dark matter and antimatter in20years. Heat pipes with axial "Ω"-shaped grooves are designed and applied in AMS-02. With the application of those heat pipes, the thermal control system becomes the most stable one of all subsystems. So far, the heat transfer characteristics by theoretical analysis and experimental study of this kind of heat pipe are rarely known. To optimize the heat transfer performance and its structure, it is necessary get better understanding of its heat transfer characteristics and heat transfer mechanism. By adopting both experimental and numerical simulation methods, the heat transfer mechanism in the heat pipe is analyzed.By using the UDF, and concerning the changing of fluid property, the simulation of the heat pipe is accomplished. Results show that the phase transition processes in the condensation section and liquid pool in evaporator section are filmwise condensation and boiling especially. Moreover, it is pointed out that under high heat flux condition, the flow pattern in the evaporator section is that bubbles and liquid flow together as a mixture. Besides, the temperature distribution and thermal resistance values from the results of simulation agree well with that of experimental data. The curve of thermal resistance of heat pipe declines with the increase of input power, and becomes more and more flat. Within the scope of the calculations, the maximum heat transfer capacity of heat pipe increases with the working temperature increasing.Without the proprietary intellectual property rights and technology support of this heat pipe, quantity production will not be available. So a series of processing technology is developed, and the manufacturing process is built. At the same time, by developing and improving the cleaning process, ultrasonic technology is introduced to improve the cleaning in micro wick. A filling system with liquid ammonia as the measuring object is specially designed, which can avoid the measurement problem caused by the gasification of ammonia, and a flow meter with high sensitivity is used to ensure the filling accuracy of±0.01g. Encapsulating technology of the heat pipe is developed which improves the quality of the encapsulation. It has been proved that the heat pipe processing technologies introduced specially can greatly improve the manufacturing quality. Besides, the heat pipes show good performance with some simple tests.Experiment table for heat transfer performances of the grooved heat pipes is built. To test heat transfer performance of heat pipe at low working temperatures, the cooling system is designed by using conduction oil as cooling fluid. Besides, the lowest temperature of cold source is-55℃and the lowest working temperature of heat pipe is-4℃. The working temperature range of heat pipe applied on the AMS is-20～50℃and the operating temperatures of most electronic equipments maintain at near0℃Conventional heat pipe test tables can only make it available to carry out experimental studies with the working temperature is higher than the room temperature. So it is impossible to reflect the heat transfer characteristics of heat pipe in the whole range of working temperature. Most of the working temperatures can be carried out with the experimental table designed especially.During the experiments, the characteristic of dynamic response of heat pipe responded to the heat load has been tested. From the experimental data, it can be observed that the performances of startup and shutdown are excellent. In addition, heat pipes with higher heating power, small filling rate and length will respond to heat load changing faster. Furthermore, analysis of the steady state characteristic of the heat pipe is conducted. The distributions of axial temperatures vary with the working temperatures, input powers and heat pipe inclination angles are also demonstrated. Results show that the temperature of adiabatic section is so uniform. The maximum and minimum temperatures of the heat pipes present in transition area between the evaporator section and the adiabatic section and area between the condensation section and the adiabatic section especially. Moreover, input power and filling rate affect the axial temperature differences of heat pipes obviously. Then, the performance of heat pipe working under inverse gravity was researched, which demonstrated the heat pipe can be with a certain ability of work under inverse gravity.Then the variation of the heat transfer coefficients of evaporation and condensation the total thermal resistance and the coefficient of equivalent heat conductivity is discussed, which caused separately by the change of working temperature, input power, inclination angle and filling rate. Results show that with the increasing input power and working temperature, heat transfer ability of heat pipe has been improved. Inclination angle has different influences on the heat transfer performance of the evaporator section and condensation section. There is an optimal heat pipe inclination angle which is60°for the total thermal resistance and the coefficient of equivalent thermal conductivity of heat pipe. Filling rate has a bigger influence on the heat transfer coefficient of evaporator section than that of condensation section. For overall heat transfer performance, the best filling rate is120%. Moreover, the influence of heat pipe length on the thermal resistance and the coefficient of equivalent heat conductivity were discussed. Results show the lengths of evaporator section and condensation section play a decisive role on the overall heat transfer performance. Finally, with a certain axial temperature difference, the maximum heat transfer capacities of the heat pipe under different working temperatures are measured. The maximum heat transfer capability has a peak value when the working temperature is20℃. In conclusion, heat pipes tested in those experiments own excellent dynamic response to the variation of heat load, small heat resistance and good isothermal characteristics.Finally, three-dimensional numerical model of the grooved heat pipe is built and simulations are carried out. The effects of structural parameters such as wick slot width, wick diameter, vapor core diameter and groove number are included. Structural parameters of heat pipe have an interrelation and mutual restriction relationship with each other. And the influences of parameters on the heat transfer performance are different. Analyzing the degree of the parameters influencing on heat transfer performance of heat pipe, they are wick diameter, groove number, the slot width and the vapor core diameter. The optimum structural parameters of heat pipe should be determined by the aim of achieving maximizing heat transfer capability or minimizing thermal resistance. |
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