Experimental study on flow condensation of mixture in a hydrophobic microchannel. (January 2017)

• Record Type: Journal Article
• Authors: Zhang, Chengbin; Shen, Chaoqun; Chen, Yongping
• Is Part Of: International journal of heat and mass transfer. Volume 104(2017:Jan.)
• Page Start: 1135
• Page End: 1144
• Publication Date: 2017-01
• Subjects: Condensation -- Microchannel -- Mixture -- Flow pattern; Heat -- Transmission -- Periodicals; Mass transfer -- Periodicals; Chaleur -- Transmission -- Périodiques; Transfert de masse -- Périodiques; Electronic journals; 621.4022
• DOI: 10.1016/j.ijheatmasstransfer.2016.09.029
• Languages: English
• ISSNs: 0017-9310

Abstract

Highlights: Flow condensation of mixture in a hydrophobic microchannel is investigated. Role of surface wettability and ethanol concentration on condensation is presented. Droplet-streak flow, droplet-injection flow, annular-streak flow are observed. A lower ethanol concentration cause the injection location move toward the outlet. Surface hydrophobic modification is benefit for flow condensation heat transfer. Abstract: The condensation flow patterns of ethanol–water mixture in a wide range of ethanol mass concentration inside a hydrophobic microchannel is experimentally studied via a high speed imaging system. The effects of channel surface wettability and ethanol concentration on flow condensation are compared and discussed. The experimental results indicate that the surface hydrophobic modification and ethanol concentration play a significant role in the flow condensation of mixture in a microchannel. The droplet condensation appears almost the whole two-phase flow region when the water steam is the main component, in which the droplet flow, droplet-streak flow, droplet-annular flow, droplet-injection flow and droplet-slug/bubble flow occur sequentially in a hydrophobic microchannel. With increasing ethanol concentration, the droplet-slug/bubble flow after droplet-injection flow disappears and is replaced by the pure slug/bubble flow. When the ethanol vapor is the main component, the droplet condensation almost disappears, and the annular-streak flow, annular flow, injection flow and slug/bubble flow appear sequentially along the flow direction. Both an increase in vapor Reynolds number and a decrease in ethanol concentration cause the injection location move toward the channel outlet. In addition, the surface hydrophobic modification introduces the droplet condensation, which is beneficial for the flow condensation heat transfer.