1. Experimental study was performed using water as working medium to investigate the flow instability in a vertical narrow annuli with both subcooled and saturated boilings. 以水为工质,分别在过冷和饱和条件下对竖直窄环隙流道进行了自然对流沸腾流动不稳定性实验,观测到了窄隙流道饱和沸腾时所特有的蒸干型流动不稳定性。