AbstractA model which describes the operation of a fibrous bed coalescer is presented. From this model, a theoretical equation can be derived for the filter coefficient, λ, at small velocities where the effect of turbulence is negligible. This expression which considers the void fraction of the bed, ϵ, the drop diameter, dp, the average saturation, Sm, the fiber diameter, dP, and the effective fiber diameter dfe, is:where β is the fraction of collisions which lead to coalescence. At larger velocities, a suitable empirical equation is obtained by multiplying the above expression by the square root of the velocity at which the filter coefficient begins to decrease divided by the superficial velocity. These equations describe the data of various workers.A method of obtaining the average saturation in a fibrous bed is presented. A possible correlating equation is found to be:where U is the superficial veloci