新型外分液结构调控水平管间歇流流型

Intermitted flow pattern modulation by outward phase separation

相变传热广泛存在于换热领域,而两相流中的厚液膜是恶化相变传热的根本原因。提出在换热管壁面设计新型网状外分液结构,利用金属网进行间歇流气液非能动相分离,从而调控流型、强化传热。通过搭建空气-水水平管冷态实验台,证实当间歇流经过外分液结构时,气体在表面张力作用下被金属网孔拦截,液桥和厚液膜则被分离出换热管,使管内液相减少,气相汇聚,有效增大气相与管壁的接触概率;多级分液后气液两相长度比呈振荡上升,甚至将间歇流调控为分层流。减小液速或增大气速,分液效果越好,间歇流最终转变为分层流所需经历的外分液级数越少,预期此结构可显著提高相变传热效果。

Phase transition heat exchange is widely used in heat transfer. The thick liquid film formed during phase transition is the reason for worsening condensation heat transfer. The passive phase separation concept using mesh construction on the pipe wall was proposed to modulate the flow pattern for the first time. In order to verify the novel concept, air-water two-phase flow experiment was performed. It was found that part of the liquid could be separated and removed from the pipe and the contact area between air and tube wall was increased. The length ratio of gas and liquid increased oscillatorily after multi-stage modulation, and furthermore, slug flow pattern changed to stratified flow. With the decrease of liquid velocity or the increase of gas velocity the modulation effect was enhanced. According to the result of the adiabatic two-phase flow pattern modulation, it was expected that the structure would significantly enhance phase transition heat transfer performance.