相分离概念调控水平管分层流流型

Stratified flow pattern modulation by phase separation concept

冷凝传热广泛存在于各种冷凝器中,传统冷凝管内厚液膜将蒸汽与冷壁面隔开,是恶化冷凝传热的根本原因。提出采用非能动相分离概念,在冷凝管内设置柱状金属丝网,管壁与丝网之间形成环形间隙。液体在表面张力作用下被捕获到丝网内,气相在环隙内流动,使气液相分布与传热协同。为验证这一新颖学术思想,开展空气-水两相流实验,获得相分离概念调控水平管内分层流实验结果。发现当水平管内具有一定液位高度时,全部液体被捕获到网内流动,管壁完全被气相覆盖,实现'气托液'模式。水平管内液位较低时,部分液体被捕获至丝网内,气相与管壁接触面积增大。按以上相分离方法对分层流的调控,在发生冷凝传热时,预期可实现高强度冷凝传热。

Condensation heat transfer is widely applied in various condensers.The thick liquid film separates the vapor from the cold wall surface,which causes worsening condensation heat transfer.The passive phase separation concept which inserts a mess cylinder to the condenser tube was proposed,the insert mesh cylinder divide condenser tube into a centre region to flow liquid and an annular region to flow gas to modulate the flow pattern for the first time.In order to verify the novel concept,the air-water two-phase flow experiment was performed,and the experimental results on the stratified flow pattern modulation by the phase separation concept was reported.It was found that all the liquid could be captured into a mesh cylinder（MC）installed in the condenser tube when the liquid level was relatively higher in the horizontal tube,forming the ＂gas-floating-liquid＂ mode.When the liquid height was small in the horizontal tube,partial liquid could be sucked by the MC,and the contact area between gas and tube wall was increased.According to the result of the adiabatic two-phase flow pattern modulation,it was expected that the contact area between vapor and cold tube wall was increased,yielding the super-enhanced condensation heat transfer when condensation heat transfer occurred.