摘要
本文对不同重力环境中水平管内冷凝气液两相流动与传热现象的研究现状进行了全面评介,重点关注于航天应用中的小管径、低流量和以氨为工质的情形,以及部分重力条件下冷凝现象中的重力效应.冷凝现象中管壁四周液膜的存在,导致水平管内冷凝气液两相流与沸腾或绝热气液两相流在构型上存在着明显的不同,表面张力的作用增大,向波状和分层流转换所对应的临界Bond数也随之增大,进而使小管径、低流量水平管内冷凝气液两相流动与传热现象中的重力效应减弱,甚至可以忽略不计.实验发现该情形中摩擦压降要小于基于常规气液两相流实验数据的经验关联式的预测结果,而更接近光滑环状流情形;对冷凝两相传热系数的预测,只有采用基于空隙率与界面剪切率相互耦合的模型,才能够给出较好的结果.
Studies on horizontal in-tube condensation flow and heat transfer in different gravity conditions are reviewed, with focus concentrated on the case of small scale tube, for low flow rate of ammonia, which is a routine practice in space applications. Gravity influence on in-tube condensation in partial gravity conditions are discussed in detail. Condensate film on the inner perimeter in horizontal in-tube condensation leads to the differences of its flow configuration from forced boiling and adiabatic two-phase gas-liquid flow, which enhances the effects of surface tension and increases the value of the critical Bond number with regards to the transition to wavy and stratified flow regimes. Thus, the influence of gravity on flow and heat transfer in horizontal in-tube condensation with small scale tube and low flow rate will be weakened, even be come negligible. It was found that the measured frictional pressure drops in these cases are close to the predictions given by smooth annular flow model, which are smaller than the predictions by empirical correlations based on the experimental data of two-phase gas-liquid flow at conventional conditions. Better predictions are obtained only by using a method based on a coupling of the void fraction with the interfacial shear rate.
出处
《力学进展》
EI
CSCD
北大核心
2011年第6期702-710,共9页
Advances in Mechanics
关键词
微重力
管内冷凝
气液两相流
压降
传热系数
microgravity, in-tube condensation, two-phase gas-liquid flow, pressure drop, heat transfer coetficient
