Steam Condensation on Various Gold Surfaces

Abstract

Gold surfaces were investigated as promoters of dropwise condensation (DWC) of steam at atmospheric pressure. Very high heat fluxes at low ΔT’s may be achieved in this manner. Seven gold electroplating baths, one electroless immersion gold bath, and vacuum vapor deposition of gold were used. Five surface preparations for pure gold were tested. Gold deposits ranged in thickness up to 20,000 A.U. Auger electron spectroscopy and scanning electron microscopy were used to describe the surfaces chemically and physically. Deposits from the bright pure gold plating baths and the “acid, hard” baths promoted DWC. Deposits from alloyed baths, the ultrapure bath, and vapor deposition gave mixed or filmwise condensation. Two surface preparations on solid gold gave DWC, one gave mixed, and two gave filmwise condensation. The results indicate that gold provides an oxide-free surface which adsorbs trace organics from the surroundings. These promote DWC.