Mixed dropwise-filmwise condensation heat transfer on biphilic surface. (April 2020)

• Record Type: Journal Article
• Authors: Xie, Jian; She, Qingting; Xu, Jinliang; Liang, Cong; Li, Wenxiao
• Is Part Of: International journal of heat and mass transfer. Volume 150(2020)
• Publication Date: 2020-04
• Subjects: Condensation -- Heat transfer enhancement -- Biphilic surface -- Droplet detachment -- Wettability; Heat -- Transmission -- Periodicals; Mass transfer -- Periodicals; Chaleur -- Transmission -- Périodiques; Transfert de masse -- Périodiques; Electronic journals; 621.4022
• DOI: 10.1016/j.ijheatmasstransfer.2019.119273
• Languages: English
• ISSNs: 0017-9310

Abstract

Highlights: The proposed dropwise-filmwise condensation model includes comprehensive drop detachment modes. Only considering the double-side-suction mode underpredicts the heat transfer coefficients. Optimal condition exists due to competition between heat transfer and area ratio of hydrophobic region. Optimal width of hydrophobic stripe is mainly dominated by geometrical parameters of δ p and W FWC . Biphilic surface does not always enhance heat transfer if geometrical parameters are not properly selected. Abstract: Condensation heat transfer on biphilic surface is investigated. The surface periodically populates hydrophobic stripes each having a coating layer thickness δ p and a width W DWC, and hydrophilic stripes each having a width W FWC . The proposed model includes dropwise condensation on hydrophobic stripe, filmwise condensation on hydrophilic stripe, and droplet detachment radius r max criterion for heat-mass coupling between the two wettabilities regions. The r max is the minimum of detachment radii determined by droplet removal modes of double-sides-suction DSS, one-side-suction OSS and sliding, where DSS is a special case of OSS for droplet located at hydrophobic stripe centerline. Simulation results matched the measured heat transfer data well. Optimal width of hydrophobic stripe W DWC o is found to be dominated by δ p and W FWC, but other parameters weakly influence W DWC o . Interfaced by a δ p − W FWC transition curve, a heat transfer regime map is presented to contain Regime I for possible heat transfer enhancement and Regime II for heat transfer deterioration. Regime I enhances heat transfer if W DWC approaches W DWC o, but may deteriorate heat transfer if W DWC deviates W DWC o too much. The maximum heat transfer enhancement ratio is 1.67 compared with purely hydrophobic surface. Regime II always deteriorates heat transfer. Our work provides a general guideline to design biphilic surface for performance improvement. Graphic abstract: Image, graphical abstract