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对常压下竖直环隙流道内沸腾换热启动阶段壁温的瞬态变化特性和流动不稳定性进行了实验研究。结果表明环隙流道壁温变化经历跃升回落、各截面平均温度基本不变和快速上升三个阶段，存在强烈的流动不稳定性和壁温波动，并伴随着局部干湿交替现象。产生流动不稳定性的主要原因是流道中间歇生成长聚合汽泡，引起介质的突然加速、停滞或倒流。影响壁温波动的主要因素有环隙宽度、加热热流密度、初始水温、进出口附近大容积液体的过冷度及加热面吸附的不凝性气体等。
The transient characteristics of wall temperature and the instability of flow at the start-up phase of boiling heat transfer in a vertical annular channel were investigated experimentally. The results show that the wall temperature of the annular channel experiences a jump and fall, the average temperature of each section is basically unchanged and rapid rise in three stages, there is a strong flow instability and wall temperature fluctuations, accompanied by alternating local wet and dry phenomenon. The main reason for the instability of flow is the intermittent formation of polymerization bubbles in the flow channel, causing sudden acceleration, stagnation or backflow of the medium. The main factors influencing wall temperature fluctuation are annular width, heating heat flux density, initial water temperature, supercooling of large volume liquid near the inlet and outlet and non-condensable gas adsorbed on the heating surface.