竖直细管内高速空气-过冷水环状两相流的蒸发-对流耦合传热特性

EVAPORATION AND CONVECTION COUPLED HEAT TRANSFER FOR ANNULAR TWO-PHASE FLOW OF WATER AND AIR IN A SMALL VERTICAL TUBE

通过数值计算研究了竖直细小传热管内高速空气-过冷水非沸腾环状两相流的传热传质特性。计算结果表明:在细小管内壁上过冷水形成非常薄的液膜,壁面热流密度可以分为液膜吸热,液膜蒸发和气相(湿空气)吸热3部分。 在管内下部的环状流区域内,液膜蒸发换热是支配性的传热方式,并具有十分强的换热能力。 数值计算指出即使在高热流密度条件下管壁温也能保持在较低范围。 计算结果较好地预示了过去的实验结果。

A numerical calculation based on the two-phase flow boundary layer model is applied to simulate the evaporation and convection coupled heat transfer charac-teristics for the non-boiling annular two-phase flow of air and subcooled water through a small vertical heated tube with uniform wall heat flux. The computational results show that water carried into the tube by air flow attaches to the wall and forms a very thin water film. The wall heat flux supplies the evaporation heat flux of the water, and the sensible heat absorbed by water and mixed gas, respectively. In the downstream zone of the tube, the evaporative heat transfer of the water film is dominant and its heat transfer ability is remarkable. The computational results show also that the wall temperature distributions lie in a low range even at quite high wall heat flux. The numerical simulations well support the previous experimental data.