A. Introduction

Fog can occur when a vapor or a gas-vapor mixture is cooled below its saturation temperature, small condensate droplets (0.1 - 40 μm) being formed by condensation of the vapor. Under certain operating conditions of surface condensers, fog may occur, condensation occurring not only on the cooled surface but within the vapor space as well.

B. Supersaturation

Consider a droplet of liquid in its own vapor. Because of surface tension effects Temperley (1956), Amelin (1967), for equilibrium the vapor pressure (p_v) exceeds the normal saturated value (p_v,sat) according to the equation

\[\label{eq1}p_{\nu} - p_{\nu, {\rm sat}} = \frac{\rho_{\nu}}{\rho_{Q} - \rho_{\nu}}\frac{2_{\sigma}}{r}\tag{1}\]