scholarly journals A Review of Research on Dropwise Condensation Heat Transfer

2021 ◽  
Vol 11 (4) ◽  
pp. 1553
Author(s):  
Xuechao Hu ◽  
Qiujie Yi ◽  
Xiangqiang Kong ◽  
Jianwei Wang
Keyword(s):  
Heat Transfer ◽  
Theoretical Models ◽  
High Heat ◽  
Condensation Heat Transfer ◽  
Formation Mechanisms ◽  
Transfer Model ◽  
Dropwise Condensation ◽  
High Heat Transfer ◽  
Nucleation Sites ◽  
Enhancing Heat Transfer

Dropwise condensation is considered to be an effective method of enhancing heat transfer due to its high heat transfer performance. However, because the effect of dropwise condensation is affected by many complex factors, there is no systematic review summarized on the law of dropwise condensation heat transfer by scholars. In this paper, the main methods and problems of promoting dropwise condensation were reviewed based on the dropwise condensation mechanism and theoretical model. The three different hypotheses about the mechanism of dropwise condensation and the heat transfer model of dropwise condensation based on the hypothesis of nucleation sites were summarized. The methods for promoting dropwise condensation and the problems that influence dropwise condensation heat transfer are introduced in this paper. The research showed that many researchers focused on how the surface fabricated forms dropwise condensation rather than whether it enhances heat transfer. In this paper, we point out that the droplet shedding rate is the key to enhancing dropwise condensation heat transfer. Much more research on droplet formation mechanisms and theoretical models of different surfaces is supposed to be carried out in the future.

scholarly journals Enhanced condensation heat transfer using porous silica inverse opal coatings on copper tubes

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Solomon Adera ◽  
Lauren Naworski ◽  
Alana Davitt ◽  
Nikolaj K. Mandsberg ◽  
Anna V. Shneidman ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Porous Silica ◽  
High Heat ◽  
Condensation Heat Transfer ◽  
Inverse Opal ◽  
Dropwise Condensation ◽  
High Heat Transfer ◽  
The Heat Transfer Coefficient

AbstractPhase-change condensation is commonplace in nature and industry. Since the 1930s, it is well understood that vapor condenses in filmwise mode on clean metallic surfaces whereas it condenses by forming discrete droplets on surfaces coated with a promoter material. In both filmwise and dropwise modes, the condensate is removed when gravity overcomes pinning forces. In this work, we show rapid condensate transport through cracks that formed due to material shrinkage when a copper tube is coated with silica inverse opal structures. Importantly, the high hydraulic conductivity of the cracks promote axial condensate transport that is beneficial for condensation heat transfer. In our experiments, the cracks improved the heat transfer coefficient from ≈ 12 kW/m2 K for laminar filmwise condensation on smooth clean copper tubes to ≈ 80 kW/m2 K for inverse opal coated copper tubes; nearly a sevenfold increase from filmwise condensation and identical enhancement with state-of-the-art dropwise condensation. Furthermore, our results show that impregnating the porous structure with oil further improves the heat transfer coefficient by an additional 30% to ≈ 103 kW/m2 K. Importantly, compared to the fast-degrading dropwise condensation, the inverse opal coated copper tubes maintained high heat transfer rates when the experiments were repeated > 20 times; each experiment lasting 3–4 h. In addition to the new coating approach, the insights gained from this work present a strategy to minimize oil depletion during condensation from lubricated surfaces.

A Heat Transfer Model of Dropwise Condensation Underneath a Horizontal Substrate

2011 ◽  
Vol 199-200 ◽  
pp. 1604-1608
Author(s):  
Yun Fu Chen
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Contact Angle ◽  
Fractal Model ◽  
Condensation Heat Transfer ◽  
Droplet Growth ◽  
Transfer Model ◽  
Dropwise Condensation ◽  
Small Contact Angle ◽  
Horizontal Substrate

For finding influence of the condensing surface to dropwise condensation heat transfer, a fractal model for dropwise condensation heat transfer has been established based on the self-similarity characteristics of droplet growth at various magnifications on condensing surfaces with considering influence of contact angle to heat transfer. It has been shown based on the proposed fractal model that the area fraction of drops decreases with contact angle increase under the same sub-cooled temperature; Varying the contact angle changes the drop distribution; higher the contact angle, lower the departing droplet size and large number density of small droplets; dropwise condensation translates easily to the filmwise condensation at the small contact angle ;the heat flux increases with the sub-cooled temperature increases, and the greater of contact angle, the more heat flux increases slowly.

Effect of Nano-Structured Surface on Meniscus Evaporation at Nanoscale

2010 ◽  
Author(s):  
Shalabh C. Maroo ◽  
J. N. Chung
Keyword(s):  
Heat Transfer ◽  
High Heat ◽  
Bubble Nucleation ◽  
Heater Surface ◽  
Transfer Coefficients ◽  
Transfer Rates ◽  
Heat Transfer Coefficients ◽  
High Heat Transfer ◽  
Enhancing Heat Transfer ◽  
To Come

Evaporation of a nanoscale meniscus on a nano-structured heater surface is simulated using molecular dynamics. The nanostructures are evenly spaced on the surface and rectangular-shaped with a length and height of 0.41 nm and 0.96 nm respectively, and stretching throughout the width of the domain. The simulation results show that the film breaks during the early stages of evaporation due to the presence of nanostructures and no non-evaporating film forms (unlike a previous simulation performed in absence of nanostructures where non-evaporating film forms on the smooth surface). High heat transfer and evaporation rates are obtained. We conclude that heat transfer rates can be significantly increased during bubble nucleation and growth by the presence of nanostructures on the surface as it breaks the formation of non-evaporating film. This will cause additional chaos and allow the surrounding cooler liquid to come in contact with the surface enhancing heat transfer coefficients.

Conduction through Droplets during Dropwise Condensation

1973 ◽  
Vol 95 (1) ◽  
pp. 12-19 ◽  
Author(s):  
Charles J. Hurst ◽  
Donald R. Olson
Keyword(s):  
Heat Transfer ◽  
Finite Element Analysis ◽  
Experimental Investigation ◽  
High Heat ◽  
Dropwise Condensation ◽  
Lower Side ◽  
Element Analysis ◽  
High Heat Transfer ◽  
Very High ◽  
Good Agreement

An experimental investigation was undertaken in which dropwise condensation was caused to occur on the upper side of a 0.001-in-thick horizontal copper condensing surface. The lower side of the condensing wall was convectively cooled, and the cooled-side temperatures under growing droplets were measured using infrared-radiation techniques. Temperature measurements showed good agreement with the results of a finite-element analysis of the droplet and condensing surface. Both experimental and analytical results pointed to the existence of an area of very high heat transfer right around the droplet perimeter, and to the importance of the condensing wall as a heat-diffusing mechanism in dropwise condensation.

Condensation of R-134a on Horizontal Enhanced Tubes Having Three-Dimensional Roughness

2016 ◽  
Vol 24 (02) ◽  
pp. 1650013 ◽  
Author(s):  
Nae-Hyun Kim
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
High Heat ◽  
Condensation Heat Transfer ◽  
Transfer Coefficients ◽  
Process Industries ◽  
High Heat Transfer ◽  
Enhanced Tubes ◽  
R 134A ◽  
Geometric Variation

Enhanced tubes are widely used in shell and tube condensers of refrigeration, air-conditioning and process industries because of their high heat transfer performance. In this study, condensation heat transfer tests were conducted for four three-dimensional enhanced tubes having different fin density and fin height using R-134a. The satuartion temperature was 40[Formula: see text]C. The heat transfer was significantly enhanced by the present enhanced geometry. At 5[Formula: see text]K wall subcooling, the enhancement ratio is 6.3 for 1654[Formula: see text]fpm, 4.6 for 1575[Formula: see text]fpm, 4.0 for 1496[Formula: see text]fpm and 3.3 for 1102[Formula: see text]fpm tubes. Within the geometric variation of the present study, the condensation heat transfer coefficient increased with the increase of fin density and of fin height. The heat transfer coefficients of the 1654[Formula: see text]fpm tube were approximately the same as those of the commercial three-dimensional enhanced tube Turbo-C.

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