竖直管内降膜-高速空气环状两相流的蒸发换热特性理论分析

通过理论分析，研究了竖直传热管内降膜－高速空气环状两相流的蒸发换热特性。结果表明，在直径2－3mm的细小管内，重力的影响可以忽略，气液间摩擦力起支配作用；在直径10mm左右的普通尺寸管内，重力的影响不能忽略；在直径更大的管内，重力的影响起支配作用。对定热流密度条件下的换热特性得到了数值解并整理成简化计算公式。研究结果对竖直传热管内水－空气两相流蒸发换热特性提供了一种基本的流动和传热规律。

Theoretical Study for Evaporative Heat Transfer of Annular Two-Phase Flow of Liquid Film and High-Velocity Air in Vertically Heated Tubes

A theoretical analysis was carried out for evaporative heat transfer of annular two phase flow of liquid film and high velocity air in vertically heated tubes. The analytical results show that the gravitational force can be neglected for small tubes whose diameter is about less than 3 mm. The evaporative heat transfer is only governed by a friction force in the small tubes. For relatively large tubes, the evaporative heat transfer is governed by both friction force and gravitational force. The numerical solutions of heat transfer characteristics were obtained and the simplified correlations were also got for constant heat flux conditions. In this study, the primary flow and evaporative heat transfer characteristics were provided for annular water air two phase flow in vertically heated tubes.