Researches On Manufacturing Processes And Experimental Performance Analyses Of Small Axially Grooved Heat Pipes

Heat pipe is a kind of heat transfer device that utilizes the phase change of its internal working liquid. It has many essential characteristics that make it useful in a wide applications and this is also true in space aspect. Major characteristics of heat pipes are high thermal conductivity, excellent isothermal property, variability of heat fluxes density, high reliability, and etc. Based on the platform of the international cooperative project named Alpha Magnetic Spectrometer 02 (AMS-02) in which Shandong University is one of the participates, aluminum-ammonia axially grooved heat pipes are designed and manufactured in Shandong University; theoretical analyses and experimental investigations are also performed on them to check their heat transfer performances.Heat pipe design is determined by application requirements and working conditions of the project AMS-02. Major designs include four aspects: selection of the heat pipe shell material and the working fluid, design of the wick and the shell structure, verification of the shell intension and determination of the working fluid charging quantity. In this paper, ammonia is chosen as the working fluid and aluminum as the shell material; the charging quantity is 19.1 gram per unit heat pipe length (1 meter). The manufacturing process is analyzed and designed in this paper, which is mainly consisted of eight steps that are mechanical machining, cleaning, desiccation, assembly, checking for leakage, outgassing, charging and sealing.After the successful manufacture of heat pipes, theoretical analyses are first done based on the Cotter heat pipe theory. Theoretical analyses mainly contain the heat transfer mechanism of axial grooved heat pipes, calculation of heat transfer limitations under different working temperatures as well as the obtaining of the maximal leaning angle on the condition of an upper-located heat source.Experiments are carried out to evaluate heat transfer characteristics and performances of the finished heat pipe. Experimental results describe the manufactured heat pipe's start-up and the steady-state characteristics; the effect of thermal loads, cooling water flow rate and leaning angle on the heat pipe working temperature is analyzed. The relationship and regularity between the working temperature, thermal loads, leaning angle and the heat pipe's evaporation heat transfer coefficient, condensation heat transfer coefficient, equivalent heat transfer coefficient are also obtained in this paper.