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A comprehensive understanding of enhanced condensation heat transfer using phase separation concept

Xie, Jian, Xu, Jinliang, Liang, Cong, She, Qingting, Li, Mingjia
Energy 2019 v.172 pp. 661-674
Reynolds number, droplets, heat transfer, liquids, porosity, separation, vapors
A comprehensive analysis of enhanced condensation with phase separation concept is presented, for which mesh-membrane-tube (MMT) is suspended in a tube. A twill Dutch weaved mesh screen and two plain Dutch weaved mesh screens are used to fabricate MMT. Our study reveals that liquid leakage across MMT not only keeps better condensation on condenser wall, but also decreases pressure drop rise penalty. To modulate stratified-flow, the #1 MMT with smallest dp has the largest capillary force to pump liquid towards core region to expose more condenser surface with vapor, where dp is pore diameter. To modulate annular-flow, finest mesh wires of #1 MMT ensure the best wetting to liquid to prevent condenser wall from being impacted by satellite droplets. These mechanisms explain the best performance of #1 MMT, reaching a maximum heat transfer enhancement ratio of 1.82. The three MMTs share a single curve of nozzle discharge coefficient versus Reynolds number. The similar performance of #2 and #3 MMTs is due to identical dp/φ, where φ is mesh open porosity. Fine mesh wires and small mesh pores are suggested to enhance condensation heat transfer. MMT are recommended to be used in condenser tube upstream when vapor mass qualities larger than 0.1.