Effect of Microstructures on Superhydrophobic and Slippery Lubricant-Infused Porous Surfaces During Condensation Phase-Change

2018 ◽  
Author(s):  
Daniel Orejon ◽  
Yota Maeda ◽  
Fengyong Lv ◽  
Peng Zhang ◽  
Yasuyuki Takata
Keyword(s):  
Heat Transfer ◽  
Surface Structure ◽  
Heat Transfer Performance ◽  
Contact Angle Hysteresis ◽  
Jumping Performance ◽  
Porous Surfaces ◽  
Transfer Properties ◽  
Surface Energy Analysis ◽  
Effect Of Surface ◽  
Oxidation Growth

Superhydrophobic surfaces (SHSs) and slippery lubricant-infused porous surfaces (SLIPSs) are receiving increasing attention for their excellent anti-icing, anti-fogging, self-cleaning and condensation heat transfer properties. The ability of such surfaces to passively shed and repel water is mainly due to the low-adhesion between the liquid and the solid surface, i.e., low contact angle hysteresis, when compared to hydrophilic or to hydrophobic surfaces. In this work we investigated the effect of surface structure on the condensation performance on SHSs and SLIPSs. Three different SHSs with structures varying from the micro- to the nano-scale were fabricated following easy and scalable etching and oxidation growth procedures. The condensation performance on such surfaces was evaluated by optical microscopy in a temperature and humidity controlled environmental chamber. On SHSs important differences on the size and on the number of the coalescing droplets required for the jump to ensue were found when varying the surface structure underneath the condensing droplets. A surface energy analysis is proposed to account for the suppression of the droplet-jumping performance in the presence of microstructures. On other hand, by impregnating the same SHSs with a low surface tension oil, i.e., SLIPSs, the adhesion between the condensate and the SLIPSs can be further reduced. On SLIPSs slight differences on the droplet density over time and shedding performance upon the inclusion of microstructures were observed. Droplets were found to shed faster and with smaller diameters on SLIPSs in the presence of microstructures when compared to solely nanostructured SLIPSs. We conclude that on SHSs the droplet-jumping performance of micrometer droplets is deteriorated in the presence of microstructures with the consequent decrease in the heat transfer performance, whereas on SLIPSs the droplet self-removal is actually improved in the presence of microstructures.

A Method for Determining the Heat Transfer Properties of Foam-Fins

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Robert J. Moffat ◽  
John K. Eaton ◽  
Andrew Onstad
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Heat Transfer Performance ◽  
Electronic Cooling ◽  
Test Method ◽  
Heat Sinks ◽  
Compact Heat Exchangers ◽  
Extended Surfaces ◽  
Open Cell Foams ◽  
Transfer Properties

Metallic and graphitic open-cell foams are being used or proposed as extended surfaces (fins) in heat sinks for electronic cooling and compact heat exchangers for aircraft applications. Three parameters must be known to calculate the heat transfer performance of a foam-fin: the product hmAc* as a function of flow-rate (the convective conductance per unit volume), the product ksAk* (the effective conductive conductance as a fin), and Rbond (the effective thermal resistance between the foam and the surface to which it is attached). This paper describes a new test method, which, in conjunction with an older well established type of test, allows all three parameters to be measured using one specimen.

Effect of Surface Radiation on Conjugate Natural Convection in a Square Enclosure with a Tube at Different Locations

2013 ◽  
Vol 281 ◽  
pp. 190-196 ◽  
Author(s):  
Jian Sheng Wang ◽  
Yong Xu
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Transfer Performance ◽  
Convection Heat Transfer ◽  
Surface Radiation ◽  
Square Enclosure ◽  
Conjugate Natural Convection ◽  
Different Temperatures ◽  
Vertical Walls ◽  
Effect Of Surface

The conjugate natural convection heat transfer with and without the interaction of the surface radiation in a square enclosure was carried out by numerical simulation. The vertical walls of the square enclosure were heated with different temperatures, and the others were adiabatic. A circular tube was inserted into the square enclosure. It was observed that varied location of the tube center can lead to different motion and heat transfer intensities. In addition, surface radiation reduces the convective heat transfer in the square enclosure compared to the pure natural convection case and enhances the overall heat transfer performance.

scholarly journals Heat transfer properties of Morpho butterfly wings and the dependence of these properties on the wing surface structure

RSC Advances ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 2786-2790
Author(s):  
Mari Kawabe ◽  
Hirotaka Maeda ◽  
Toshihiro Kasuga
Keyword(s):  
Heat Transfer ◽  
Surface Structure ◽  
Wing Surface ◽  
Butterfly Wings ◽  
Blue Line ◽  
Transfer Properties ◽  
Morpho Butterfly ◽  
Red Line

The heat transfer properties of Morpho butterfly wings (red line) were higher than those of Cithaerias wings (blue line) due to their surface structure and emissivity.

Effect of surface structure and coating on the heat transfer deflection behavior in the early stage of nucleate boiling

2018 ◽  
Vol 126 ◽  
pp. 1315-1322 ◽  
Author(s):  
Hyunwoo Noh ◽  
Jin Man Kim ◽  
HangJin Jo ◽  
Hyun Sun Park ◽  
Don Koan Hwang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Surface Structure ◽  
Early Stage ◽  
Nucleate Boiling ◽  
Effect Of Surface

Effect of Surface Microstructure on Microchannel Heat Transfer Performance

2011 ◽  
Vol 133 (12) ◽  
Author(s):  
Yang Liu ◽  
Jing Cui ◽  
WeiZhong Li ◽  
Ning Zhang
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Transfer Performance ◽  
Convection Heat Transfer ◽  
Surface Microstructure ◽  
Transfer Performance ◽  
Plate Surface ◽  
Field Synergy ◽  
Field Synergy Principle ◽  
Effect Of Surface

In this paper, forced convection heat transfer occurring in microchannels with different microstructures is investigated numerically. It is found that vortices will appear in the microstructure grooves. The influence of microchannel geometries on heat transfer performance is evaluated by Nusselt number and the entrance effect is noted for all geometries. Compared with the plain plate surface, a much more moderate decrease of local Nusselt number can be found for all the grooved microstructures, indicating more uniform heat transfer intensity along the flowing direction. The results also suggest that the heat transfer performance improves with inlet Reynolds number. The V-shaped grooved microstructure possesses the highest heat transfer performance. Compared with the plain plate surface, averaged Nusselt number can be increased by about 1.6 times. Through the field synergy principle analysis, we find that it is the synergy between temperature gradient and velocity that results in different heat transfer performance for different microstructures.

Critical Heat Flux for Downward Facing Boiling on a Coated Hemispherical Surface

Volume 3 ◽  
2004 ◽  
Author(s):  
J. Yang ◽  
M. B. Dizon ◽  
F. B. Cheung ◽  
J. L. Rempe ◽  
K. Y. Suh ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Steady State ◽  
Critical Heat Flux ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Copper Coatings ◽  
Hemispherical Surface ◽  
The Right ◽  
Effect Of Surface

An experimental study was performed to investigate the effect of surface coating on the critical heat flux for downward facing boiling on the outer surface of a hemispherical vessel. Steady-state boiling experiments were conducted in the SBLB (subscale boundary layer boiling) facility using test vessels with metallic microporous coatings to obtain the local boiling curves and the local CHF limits. Similar heat transfer performance was observed for microporous aluminum and microporous copper coatings. When compared to the corresponding data without coatings, the boiling curves for the coated vessels were found to shift upward and to the right. This meant that the CHF limit and minimum film boiling temperatures were located at higher wall superheats. In particular, the microporous coatings were found to enhance the local CHF values appreciably at all angular locations explored in the experiments. Results of the present study showed that the microporous aluminum coating was very durable. Even after many cycles of steady state boiling, the vessel coating remained rather intact, with no apparent changes in color or structure. Although similar heat transfer performance was observed for microporous copper coatings, the latter were found to be much less durable and tended to degrade after several cycles of boiling.

Numerical Research on the Heat Transfer Properties of Pulsating Flow around the Vibrating Tube

2012 ◽  
Vol 594-597 ◽  
pp. 2582-2585
Author(s):  
Xiao Tao Zheng ◽  
Si Hao Nie ◽  
Jiu Yang Yu ◽  
Wei Lin ◽  
Qian Liu
Keyword(s):  
Heat Transfer ◽  
Velocity Vector ◽  
Heat Transfer Performance ◽  
Flow Direction ◽  
Surface Heat ◽  
Pulsating Flow ◽  
Field Synergy ◽  
Surface Heat Transfer Coefficient ◽  
Numerical Research ◽  
Transfer Properties

The heat transfer properties of pulsating flow around the tube with simple harmonic vibration were analyzed. The effect of the angle θ between the flow direction and the tube vibrating direction, which changes from 0° to 150°, on heat transfer properties was numerically investigated by the dynamic mesh technology of FLUENT. The results showed that the transient surface heat transfer coefficient decreases with increasing θ when amplitudes of pulsating flow or vibrating tube increase. Comparing with the still tube, the angle between the temperature gradient and the velocity vector is smaller when the tube vibrates along different directions, hence the field synergy performance is better, and the heat transfer performance is more enhanced.

An Experimental Study on Heat Transfer Performance of Iron Oxide Based Ferrofluids

2012 ◽  
Author(s):  
Evrim Kurtoglu ◽  
Alihan Kaya ◽  
Havva Funda Yagci Acar ◽  
Ali Kosar
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Performance ◽  
Solid Phase ◽  
Aqueous Media ◽  
Intermolecular Forces ◽  
Transfer Performance ◽  
Wide Range ◽  
Materials Used ◽  
Weak Intermolecular Forces ◽  
Transfer Properties

Nanofluids are colloidal compounds, where the solid phase material is composed of nano sized particles, and the liquid phase can potentially be any fluid but aqueous media are common. As a common nanofluid type, ferrofluids are formed by holding solid nanoparticles in suspension by weak intermolecular forces and may be produced from materials with different magnetic properties. Magnetite is one of the materials used for its natural ferromagnetic properties. Heat transfer performance of ferrofluids is one of the crucial properties among many others that should be analyzed and considered for their wide range of applications. For this purpose, experiments were conducted in order to characterize heat transfer properties of ironoxide based ferrofluids flowing through a microchannel. Promising results were obtained from this study, which are suggesting the use of ferrofluids for heat transfer applications can be advantageous.

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