沸腾情形下开放式毛细微槽中的干涸特性实验研究

An Experimental Study on Dryout Characteristics under Boiling Conditions in Open Capillary Microgrooves

利用高速摄像仪、CCD以及宽视场体视显微技术对液体在微槽内的润湿、蒸发和沸腾现象进行了可视化观察和描述,对发生沸腾换热现象时的竖直矩形毛细微槽群热沉中的液体沿微槽槽道方向的干涸点高度(润湿高度)进行了测量,并对微槽几何尺寸、工质等因素对润湿高度的影响进行了实验研究.实验结果表明:微槽群的高强度的强化换热特性是由薄液膜蒸发和核态沸腾换热的共同作用造成的;发生沸腾换热现象时,微槽内的液体润湿高度随着输入加热功率的增加能得到有限度地升高;一定热负荷下,微槽较深、较宽以及微槽群密度较大时液体的润湿高度较高;在微槽内发生核态沸腾的情形下,甲醇的润湿高度要远大于乙醇和蒸馏水.

Using a high-speed camera, a CCD video camera and a wide field stereo-microscope system, wetting, evaporation and boiling scenes in microgrooves are observed. And, axial dryout point （wetting height） of liquids in vertical rectangular capillary microgrooves heat sink is measured under boiling heat transfer conditions. An experimental study of the influences of microgroove＇s geometric parameters and working liquids on wetting height has been conducted. The results show that the enhanced heat transfer process in the microgrooves is induced by mutual effects of evaporating heat transfer in the extended thin liquid film region and boiling heat transfer in the intrinsic meniscus region. Wetting height increases to a certain extent as heat input power increases under boiling heat transfer conditions. The microgrooves with a deeper depth, a wider width or a higher microgroove density hold higher wetting capacity. Under boiling heat transfer conditions, Methanol has a far higher wetting capacity than ethanol and distilled water.