Mini-channel flow condensation enhancement through hydrophobicity in the presence of noncondensable gas

Chu, Xiaoyu; Morrow, Jordan A.; Derby, Melanie M.

doi:10.1016/j.ijheatmasstransfer.2017.07.029

Cited by 8 publications

(4 citation statements)

References 45 publications

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“…Therefore, reducing the channel cross sectional area helps increase vapor mass fluxes and obtain higher vapor shear rates. To investigate the potential of hydrophobic surfaces for enhancing the steam flow condensation heat transfer performance in minichannels and microchannels, some studies could be found in the literature. − In the study of Fang et al, flow visualization and heat transfer analysis of flow condensation of pure steam were performed in a rectangular microchannel, and a strong dependency of flow patterns on wall wetting properties were reported . Derby et al investigated steam flow condensation in a minichannel with various biphilic patterns for steam mass fluxes in the range of 50 to 200 kg/m 2 s and a wide range of steam qualities.…”

Section: Introductionmentioning

confidence: 99%

“…Chen and Derby extended Derby’s previous work, and their heat transfer analysis and visualization study on a minichannel revealed enhancements in the thermal performance of hydrophobic surfaces, as a result of the increased droplet mobility. Another study by Chen et al on flow condensation heat transfer inside a minichannel with a hydrophobic surface in the presence of non-condensable gases (NCG) revealed that NCG reduced the thermal performance of the system by 24–55%, which was due to the accumulation of NCG pockets on the condensing surface.…”

Section: Introductionmentioning

confidence: 99%

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Copper-Based Superhydrophobic Nanostructures for Heat Transfer in Flow Condensation

Chehrghani

Abbasiasl

Sadaghiani

et al. 2021

ACS Appl. Nano Mater.

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Superhydrophobic surfaces enhance the condensation heat transfer performance by facilitating removal of condensed droplets and coalescence-induced droplet jumping. During the last decade, studies on superhydrophobic surfaces have been mostly limited to working conditions, which are ideal for electron microscopy techniques. Therefore, the behavior of condensed droplets in the presence of a vapor flow with different vapor qualities and their implementation in flow condensation heat transfer enhancement have received rather little attention, which is the motivation behind this study. Thus, beside heat transfer analysis, we performed a visualization study on flow condensation in a minichannel and investigated droplet dynamics, including a histogram of droplet diameter distribution at different time intervals and stages of a condensation cycle consisting of nucleation growth and departure, droplet departure diameters, cycle time, and droplet number density. The droplet departure diameter decreases with steam mass flux, leading to a shift to smaller radii in droplet size distribution, which enhances condensation heat transfer. Enhancements up to 33% in the heat transfer coefficient were obtained at lower steam qualities for the tested superhydrophobic surface compared to the reference plain hydrophobic surface. We demonstrated that in addition to the high vapor shear stress exerted by the flow on the interface of the vapor and the condensed droplet, the advantage of an inherently unique water repellency feature of the nanostructured superhydrophobic surface can be utilized in flow condensation for enhancing condensation heat transfer.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Copper-Based Superhydrophobic Nanostructures for Heat Transfer in Flow Condensation

Chehrghani

Abbasiasl

Sadaghiani

et al. 2021

ACS Appl. Nano Mater.

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show abstract

“…One approach for enhancing condensation in microchannels is to coat the surface in hydrophobic substance such as Teflon, which transitions the filmwise condensation into dropwise condensation, resulting in enhancements up to 10 times, yet coatings are not always durable (Miljkovic and Wang, 2013;Chen and Derby, 2016;Chen et al, 2017;Antao et al, 2020;Hoque et al, 2022). However, durable hydrophobic coatings remain an active research area, thus condensation processes in industry are filmwise condensation instead of dropwise condensation (Ahlers et al, 2019;Chang et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Visualizing and disrupting liquid films for filmwise flow condensation in horizontal minichannels

et al. 2022

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This paper investigates the effects of hemispherical mounds on filmwise condensation heat transfer in micro-channels. Also investigated were the impacts that spatial orientation of the three-sided condensation surface (i.e., gravitational effects) on steam condensation, where the cooled surfaces were either the lower surface (i.e., gravity pulls liquid towards the condensing surfaces) or upper surface (i.e., gravity pulls liquid away from the condensing surfaces). Two test coupons were used with 1.9-mm hydraulic diameters and either a plain copper surface or a copper surface modified with 2-mm diameter hemispherical mounds. Heat transfer coefficients, film visualization, and pressure drop measurements were recorded for both coupons in both orientations at mass fluxes of 50 kg/m2s and 125 kg/m2s. For all test conditions, the mounds were found to increase condensation heat transfer coefficients by at minimum 13% and at maximum 79%. When the test section was inverted (i.e., condensing surface on the top of flowing steam), minimal differences were found in mound performance, while the plain coupon reduces heat transfer coefficients by as much as 14%. Flow visualization suggests that the mounds enhanced heat transfer due to the disruption of the film as well as by reducing the thermal resistance of the film. Pressure drops followed parabolic behavior with quality, being higher in the mound coupon than the plain coupon. No significant pressure drop differences in the inverted orientation were observed.

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“… 26 They demonstrated that the calcination temperature had considerable effect on the hydrophobic characteristic of the micro-porous layer. The condensation enhancement in a small channel with hydrophobic characteristic was studied by Chen et al 27 Dropwise condensation was observed in the hydrophobic channel, although the addition of nitrogen suppressed the nucleation rate. In the hydrophobic channel, heat transfer was enhanced significantly as compared to that corresponding to the hydrophilic channel.…”

Section: Introductionmentioning

confidence: 99%

Reversible exchange of wetting state of a hydrophobic surface via phase change material coating

et al. 2018

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Mini-channel flow condensation enhancement through hydrophobicity in the presence of noncondensable gas

Cited by 8 publications

References 45 publications

Copper-Based Superhydrophobic Nanostructures for Heat Transfer in Flow Condensation

Copper-Based Superhydrophobic Nanostructures for Heat Transfer in Flow Condensation

Visualizing and disrupting liquid films for filmwise flow condensation in horizontal minichannels

Reversible exchange of wetting state of a hydrophobic surface via phase change material coating

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