Long term testing for dropwise condensation using self-assembled monolayer coatings of n-octadecyl mercaptan

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.…”

“…It should be noted that the contact angle concept is used as a measure of the hydrophobicity of a coated surface; however, for accurate prediction of the DWC characteristics, experiments should be conducted. For example, in a study by Vemuri et al [108], stearic acid, which has a contact angle of 155º, did not show DWC mode when experiments were carried out.…”

“…Up to the 1990s, numerous dropwise condensation studies were conducted with a thin layer of a metal-organic compound or low-surface-fee-energy polymer coated flat surfaces. [80,107,108,109]. For instance, Marto et al [107] examined several polymer coatings in terms of their ability to promote and sustain dropwise condensation of steam.…”

“…Vemuri et al [108] created hydrophobic coatings through self-assembled monolayers (SAMs) of n-octadecylmercaptan and stearic acid on copper alloy circular tubes. They measured dropwise condensation heat flux on circular tube walls and reported that the condensation heat transfer rate was increased by a factor of 3 to 1.8 times depending on the operating conditions.…”

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).…”