The effect of polyvinylidene chloride coating thickness on promotion of dropwise steam condensation

Combined Visualization and Heat Transfer Measurements for Steam Flow Condensation in Hydrophilic and Hydrophobic Mini-Gaps

“…Since building steam quality was unknown, the steam entered the separation tank to remove excess liquid. A 500 W cartridge heater superheated the steam to [20][21][22][23][24][25][26][27][28][29][30] C above saturation temperature in order to determine enthalpy with measured temperature and pressure and the precondenser set the test section inlet quality. The precondenser was cooled via a constant temperature bath (Neslab RTE-221) with cooling water flowing rate measured by a Coriolis flow meter (Micro Motion TM F-series sensor and 2700 transmitter).…”

“…Heat fluxes and heat transfer coefficients in dropwise condensation on flat plates [1,[19][20][21][22] or external tubes [23][24][25][26] have been found to be 5-20 times higher than filmwise condensation for these external flows. Surface properties such as contact angle [27], surface roughness [20,28,29], and droplet state (i.e., Ref.…”

Advanced Heat Exchangers Using Tunable Nanoscale-Molecular Assembly

“…Gold and silver have been to known to consistently show excellent dropwise characteristics. However, the hydrophobic characteristics of these noble metals as DWC promoters have been controversial in the literature [9]. The noble metals initially have very high surface energy and tend to be completely wet by water.…”

“…In general, organic coatings are difficult to maintain, and require strong, long term adhesion forces between the coating and the metal substrate. Usually, the thicker the coating, the better its resistance to erosion, but due to its low thermal conductivity, thick organic coatings add to the heat transfer resistance and affects the DWC performance [9].…”

“…Their results indicated that the heat transfer coefficients of steam DWC for surfaces coating with organic films are as large as 3-8 times that of film condensation for smooth surfaces. Haraguchi and Shimada [9], proposed polyvinylidene chloride coatings as a promoter of DWC, they cleaned the condenser surface till no scratches were found then dipped in ethanol and left to air dry, after air drying the surface was coated with polyvinylidene chloride, they claimed that its processing cost was much cheaper than other methods used previously even for a large area coating surface. Hydrophobic coatin mono la ers (SAMs) on copper alloy (99.9% C enhance steam condensation thro of self-assembled monolayers (SA desirabl films that are only as thick as the composite long.…”