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流动沸腾换热是典型的两相流问题。窄通道与常规通道相比较,其流动沸腾换热系数有较大提高,换热机理也更加复杂。针对截面为250 mm×5 mm的竖直矩形窄缝通道,在低压、入口温度过冷、不同质量流速及加热功率密度的条件下,对水流动沸腾换热特性进行实验研究。通过实验分析可知:入口温度27～60℃、质量流速2.22～3.49 kg/(m2.s)及加热功率密度0～12 kW/m2对饱和沸腾起始点和过冷段长度有重要影响;高的空泡份额和通道结构的限制使汽液两相流动不稳定而影响换热系数,换热系数随着功率的增大而减小,流体进入完全对流沸腾阶段;由于实验段通道顶部结构的限制,干度的增加不会出现干涸点,换热不会得到恶化,换热系数随着功率的增大基本不变。
Flow boiling heat transfer is a typical two-phase flow problem. Narrow channel compared with the conventional channel, the boiling heat transfer coefficient has greatly increased, the heat transfer mechanism is more complex. Aiming at the vertical rectangular narrow channel with a cross section of 250 mm × 5 mm, the experimental study of water boiling boiling heat transfer was carried out under the conditions of low pressure, subcooled inlet temperature, different mass flow rate and heating power density. The experimental results show that the inlet temperature of 27 ~ 60 ℃, mass flow rate of 2.22 ~ 3.49 kg / (m2.s) and heating power density of 0 ~ 12 kW / m2 have an important effect on the initial boiling point and the length of subcooling section; Due to the restriction of the structure of the top of the passage in the experimental section, the heat transfer coefficient decreases with the increase of the power and the fluid enters the stage of complete convection boiling. , Dryness does not increase the dry point, heat will not be deteriorated, the heat transfer coefficient increases with the power of the same.