Experimental Study On The Triple-phase Contact Line And Characteristic Of Heat Transfer In Capillary Microgrooves On Vibration Conditions

The open rectangular capillary microgrooves can create enhanced evaporating heat transfer in the extended thin film region and has been used to achieve the heat exchanges with high heat transfer coefficients and high heat flux. Therefore, capillary microgrooves heat sink can be widely used in many fields, such as high power lasers, microelectronic devices and waste heat utilization in power station.The main purpose of the present thesis is to clarify the impact of different vibration parameters on the deformation of the triple-phase contact line and analyses the influence of liquid film oscillation on the characteristics of phase change heat transfer in the heat sink of capillary microgrooves experimentally, thereby gaining significant understanding in application of the micro-scale heat sink under adverse vibration.With the help of high-speed camera and a wide-field stereo-microscope, the deformation of the contact line and changes of the characteristics of the heat transfer in rectangular capillary microgrooves(made on transparent borosilicate glass) are visualized. The vibration table are built to simulate the mechanical vibration condition and distilled water is used as cooling liquid. The effects of different vibration parameters on triple-phase contact line and the heat transfer characteristics are studied, including the deformation law of the contact line in one oscillation cycle, the distribution of the liquid film and the contact line deformation under different vibration frequency and amplitude.It’s found that under vertical vibration condition, when the vibration table moves up, the liquid in the reservoir is under overweight state and the contact line is elongated; likewise, when the vibration table moves downward, the length in contact line decreases. For the microgrooves with the same size, the deformation of the triple-phase contact line is more obvious as the vibration frequency and amplitude increase. With the same vibration frequency and amplitude, the sizes of the microgrooves have a regular influence on the contact line deformation and the contact line deforms more greatly when the groove width or the groove depth increases.According to the experiment, under horizontal vibration condition, the deformation of the triple-phase contact line is small. But the distribution of the liquid film thickness changes a little. Being the same with the vertical vibration condition, the frequency, amplitude and sizes of the microgrooves have an influence on the contact line deformation. As the increase of frequency and amplitude, the deformation of the contact line along the axial direction is more obvious. Comparing with the vertical oscillation, the proportion of liquid film oscillation is much smaller. Besides, under the same vibration condition, the bigger the microgrooves size is, the more obviously the contact line shape changes.What’s more, the paper studies the effect of triple-phase contact line deformation on the characteristics of evaporating heat transfer in liquid film region. Comparing with the stationary state, the wall temperature decreases under vertical vibration condition and with the increase of the vibration frequency and amplitude, the wall temperature decreases. Besides, the amount of heat increases obviously. The vertical vibration condition has little influence on the proportion of liquid film heat transfer in the total heat transfer.