An experimental and theoretical study on the concept of dropwise condensation

Droplet condensation on polymer surfaces: A review

“…The authors found that dropwise condensation formed by using octadecanethiol SAM is a dynamic process in that the heat transfer coefficient decreases with time over 2 h. 135 Vemuri et al used SAMs of n-octadecyl mercaptan and stearic acid on copper alloy surfaces as hydrophobic coatings with the aim of enhancing steam condensation through dropwise condensation. 136 It was found that n-octadecyl mercaptan coated SAM surfaces increased the condensation heat transfer rate by a factor of about 8-times when operated under atmospheric conditions and a theoretical model was developed involving the effect of interfacial heat transfer coefficient on heat transfer rate to calculate the sweeping effect of large falling drops. 136 In a further study, Vemuri et al used 2 different types of SAM coatings (stearic acid and n-octadecyl mercaptan) for a period of more than 2600 h. An oxide layer was formed between the substrate and SAM surface to enhance the bonding ability of SAMs to the substrate and to improve the life-time of the coatings and it was concluded that n-octadecyl mercaptan SAM showed good dropwise condensation due to its covalent bonding with the substrate surface when compared to that of stearic acid SAM, which is bonded to the substrate surface by only hydrogen bonding.…”

“…136 It was found that n-octadecyl mercaptan coated SAM surfaces increased the condensation heat transfer rate by a factor of about 8-times when operated under atmospheric conditions and a theoretical model was developed involving the effect of interfacial heat transfer coefficient on heat transfer rate to calculate the sweeping effect of large falling drops. 136 In a further study, Vemuri et al used 2 different types of SAM coatings (stearic acid and n-octadecyl mercaptan) for a period of more than 2600 h. An oxide layer was formed between the substrate and SAM surface to enhance the bonding ability of SAMs to the substrate and to improve the life-time of the coatings and it was concluded that n-octadecyl mercaptan SAM showed good dropwise condensation due to its covalent bonding with the substrate surface when compared to that of stearic acid SAM, which is bonded to the substrate surface by only hydrogen bonding. 137 Leu and Wu studied the movement of a droplet on a vertical surface created by energy patterning process using 1-dodecanethoil SAM coated onto a hydrophilic silicon substrate to improve heat transfer efficiency in a vapor condensing system and obtained 10% higher heat transfer efficiency.…”

Condensation heat transfer on superhydrophobic surfaces

“…While this mode which is known as filmwise condensation 14 ( Figure 1a) is quite common, the formation of a liquid film is not desired due to the large resistance to heat transfer. Meanwhile, if a surface is coated with a low-energy non-wetting 'promoter' material (i.e., long chain fatty acid, wax, polymer coating, self-assembled monolayer) [15][16][17][18][19] , or if it naturally adsorbs hydrocarbons and impurities on its surface from the surroundings (as in the case of gold, silver, and chromium) [20][21][22] , the vapor forms discrete liquid droplets ranging in size from microns to millimeters [23][24][25] . This process is known as dropwise condensation 26 ( Figure 1b).…”

Nanotechnology for Advanced Nuclear Thermal-Hydraulics and Safety: Boiling and Condensation

“…The effects of vapor pressure on condensation heat transfer were experimentally investigated by researchers [108,112,140,141]. The trends of the previous works all agree well.…”