Prediction of Heat Transfer Coefficient for Flow Boiling in Horizontal Tubes

水平管内流动沸腾传热系数的预测

基本信息

批准号：
61550163
负责人：
YOSHIDA Suguru
金额：
$ 1.41万
依托单位：
Kyushu University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1986
资助国家：
日本
起止时间：
1986 至 1987
项目状态：
已结题

项目摘要

At low mass velocity or low quality in horizontal evaporator-tubes, the heat transfer coefficient is not uniform but varies extermely along the tube perimeter, due to the phase separation with the liquid flowing in the lower part of the tube and the vapor in the upper part. Experimental data of the local heat transfer coefficient along the perimenter of horizontal tubes for boiling R22 were obtained under the conditions of different tube diameters, pressures, mass velocities and heat fluxes in the whole quality region. The separation angle, that is, the angle measured from the bottom point of the horizontal tube to the point of separation between the wet part and the dry part of the inside perimeter, was estimated from the heat transfer data. This angle increased with an increase in mass velocity, increased or decreased with increasing quality depending on the mass velocity, and increased with a decrease in tube diameter or pressure. The characteristics of the circumferentially averaged heat transfer coefficient were explained mainly by the behavior of the separation angle. The correlation proposed previously by the authors for the heat transfer in the annular two-phase flow regime was found to be applicable to the prediction of the averaged heat transfer coefficient over the wet perimeter of the horizontal evaporator-tube, while a well-known heat transfer correlation for singlephase fluid flow was to be applicable to the averaged heat transfer coefficient over the dry perimeter. The circumferentially averaged heat transfer rate in horizontal evaporator-tubes could be predicted by using these correlations of heat transfer coefficients and the measured value of the separation angle.

在低质量速度或水平蒸发器管中质量低时，由于相位分离，液体分离，液体在管的下部和蒸气中流动，因此传热系数不是均匀的，而是沿着管周长的沿着管周长的差异。在整个质量区域的不同管直径，压力，质量速度和热通量的条件下，获得了沿水平管的局部传热系数的实验数据。从热传递数据估算了从水平管的底点到湿部分和干燥部分之间的分离点，从水平管的底部到分离点，从热传递数据估算了分离角。该角度随着质量速度的增加而增加，随着质量速度的不同而增加或减少，并且随着管直径或压力的降低而增加。圆周平均传热系数的特征主要是通过分离角的行为来解释的。作者先前在环形两相流动方案中提出的有关热传递的相关性适用于对水平蒸发器管的湿周围的平均传热系数的预测，而对单相流动的众所周知的热传递相关，适用于平均热传递系数的单相流量。可以通过使用传热系数的这些相关性和分离角度的测量值来预测水平蒸发器管中的圆周平均传热速率。