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首页> 外文期刊>Journal of Micromechanics and Microengineering >Height effect on nucleation-site activity and size-dependent bubble dynamics in microchannel convective boiling
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Height effect on nucleation-site activity and size-dependent bubble dynamics in microchannel convective boiling

机译：高度对微通道对流沸腾中成核位点活性和尺寸依赖性气泡动力学的影响

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摘要

Forced convection boiling in microchannels is studied experimentally under the uniform heat flux boundary condition. Several microchannel heat sinks with integrated temperature sensors, spanning two orders of magnitude in height 5-500 mu m, have been fabricated with designed nucleation sites on the bottom surfaces. The microchannels are capped by a glass wafer to monitor bubble activity using video microscopy. Distributed micro heater elements on the device backside are used as the heat source, while the working liquid flow rate is adjusted using a syringe pump. The boiling curves of the device temperature as a function of the input power have been measured for various flow rates. The curves for increasing and decreasing heat flux exhibit a hysteresis loop, while the conditions corresponding to the onset of nucleate boiling and critical heat flux (CHF) are clearly distinguishable. The activity of nucleation sites as well as the ensuing bubble dynamics, from incipience to departure, is found to depend on the channel height. The critical size above which a nucleation site is active, along with three aspects of bubble dynamics, namely growth rate, departure size and release frequency, have been characterized experimentally and proper control parameters have been identified.
机译：在均匀热流边界条件下，对微通道中的强制对流沸腾进行了实验研究。已制造出几个带有集成温度传感器的微通道散热器，其高度在5-500μm的两个数量级之间，并在底面上设计了成核位置。微通道被玻璃晶圆覆盖，以使用视频显微镜监控气泡活动。设备背面的分布式微型加热器元件用作热源，同时使用注射泵调节工作液体的流量。已针对各种流速测量了设备温度随输入功率变化的沸腾曲线。增大和减小热通量的曲线显示出磁滞回线，而与晶核沸腾和临界热通量（CHF）的发生相对应的条件则可以清楚地区分。发现从开始到离开，成核位点的活动以及随后的气泡动力学取决于通道高度。已经通过实验表征了临界尺寸，在该临界尺寸以上成核位点是活跃的，以及气泡动力学的三个方面，即生长速率，离开尺寸和释放频率，并且已经确定了合适的控制参数。

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