论文部分内容阅读
在管内径9.0 mm、壁厚1.5 mm、螺旋管绕径283.0 mm的立式螺旋管内,对CO2流动沸腾换热特性进行实验研究。分析热流密度(q=1.4~48.0 kW/m2)、质量流速(G=54.0~400.0 kg/(m2·s))和运行压力(pin=5.6~7.0 MPa)对内壁温分布和换热特性的影响规律。结果表明:螺旋管内壁温周向分布不均匀,单相液体以及过热蒸汽区离心力的作用使内侧母线温度最高、外侧母线温度最低,在两相沸腾区蒸汽受到浮升力作用聚集在管上部而容易发生蒸干,因此上母线温度最高,温度最低值则由离心力和浮升力的相对大小共同决定。局部平均换热系数随热流密度以及进口压力的增加而显著增加,但增大质量流速对换热系数的影响不大,表明核态沸腾是CO2在螺旋管内流动沸腾的主要传热模式而强制对流效应较弱;发现了随着热流密度增加所引起的核态沸腾强度变化以及干涸和再润湿使得换热系数随干度的变化可分成3个区域。并基于实验获得的2 124个数据点拟合两相区沸腾换热关联式。
In a vertical spiral tube with a tube diameter of 9.0 mm, a wall thickness of 1.5 mm and a spiral coil diameter of 283.0 mm, an experiment on the CO2 boiling heat transfer was carried out. The effects of heat flux density (q = 1.4 ~ 48.0 kW / m2), mass flow velocity (G = 54.0 ~ 400.0 kg / (m2 · s) Affect the law. The results show that the inner wall of the spiral tube is unevenly distributed in the circumferential direction and the centrifugal force of the single-phase liquid and superheated steam zone makes the temperature of the inner busbar the highest and the temperature of the outer busbar the lowest. Occurred evaporated, so the bus temperature is highest, the lowest temperature by centrifugal force and the relative size of the buoyancy force jointly determine. The local average heat transfer coefficient increases with the increase of heat flux and inlet pressure, but the increase of mass flow rate has little effect on the heat transfer coefficient, indicating that nucleate boiling is the main heat transfer mode of CO2 boiling in the spiral pipe and forced convection The effect is weaker; the change of nucleate boiling intensity caused by the increase of heat flux density and the change of dry heat exchange coefficient with dryness can be divided into three regions. Based on the experimentally obtained 2 124 data points, the two-phase boiling heat transfer correlation was fitted.