Study On Fundamental And Crucial Technology About The Heat Sink Unit Of Laser Thermal Management System Based On Microgrooves Phase-Change Cooling

The performance of high-power-laser output is strongly dependent on its cooling and thermal control system, i.e. thermal management level. The thermal accumulation causes the increase of laser threshold value, the decrease of laser beam quality and efficiency. This work is focused on the laser thermal management technology with microgrooves phase-change heat transfer. The characteristic of solid-liquid-vapor triple-phase contact line along the axial of rectangle capillary microgrooves is studied, which shows the wetting status of working liquid. The temperature distribution on microgrooves surface including vapor-liquid contact surface is observed with the infrared thermoviewer. The microgrooves heat sink unit is designed, which can provide a reliable cooling method for laser thermal management.In the experiment, we utilize the visualization survey technology of CCD combined with width field stereoscope microscope. The rectangular capillary microgrooves processed on transparent boroscilicate glass are fixed on an adjustable platform. The triple-phase contact line in triangle wetting region of rectangular capillary microgrooves is visualized. The image is processed and the edge is obtained. The wetting length and film thickness in triangle wetting region are determined. Finally the whole wetting length is obtained. The results show that the working liquid, the geometry size of microgrooves, tilt angle, heat flux have an significant effect on the overall wetting length and the wetting characteristic of triangle wetting region. Based on the experimental study, a theoretical study on wetting length in triangle region of rectangular capillary microgrooves is carried out. An improved theoretical model is proposed. Compared with the experimental results, it is found that our model can well predict the relation between the wetting length in triangle region and the correlation influence factors.The infrared thermoviewer is utilized to record the infrared thermal image of the heat sink with rectangular capillary microgrooves. The temperature distribution and average temperature on microgrooves surface is measured under different operating conditions. The results indicate that the heat source position has a serious influence on the microgrooves surface temperature distribution, besides the working liquid, the geometry size of microgrooves, tilt angle, heat flux.Two kinds of heat sink units are designed based on the microgrooves phase-change cooling method. One kind is the MC-MG heat exchanger for microchannels single-phase convection and microgrooves phase-change cooling system, another kind is the microgrooves evaporator for microgrooves and thermoelectricity cooler thermal control system. The experimental studies show that, the heat transfer coefficient of MC-MG heat exchanger can reach as high as 1.6×10~4W/(m~2·K), and the total thermal resistance is smaller than 0.21K/W. The MC-MG heat exchanger is important for a double-loop cooling system for light-pump high-power laser. The surface temperature of microgrooves evaporator in the MG-TEC system is lower than 25℃and fluctuates within±1℃through changing working liquid and sufficient fluid rate. It can satisfy the working condition required by laser system. By using the developed evaporator, a compact and high-heat-flux cooling system is established.