Heat transfer in dropwise condensation at low steam pressures in the absence and presence of non-condensable gas

Abstract

Measurements are reported of steam-side heat-transfer coefficients during the dropwise condensation of steam on copper surfaces promoted by montan wax and dioctadecyl disulphide, over the heat flux range 5000–30000 Btu/ft 2h and at steam pressures of 0·8–3-in mercury. The noncondensable gas concentration by volume was varied between < 1 and 15000 ppm. At low non-condensable gas concentrations, the steam-side heat-transfer coefficients varied between 10000 and 28000 Btu/ft 2h degF over the steam pressure ranges studied which would indicate that the condensation coefficient for water is at least 0·1.