Assuming the laminar flow across the filter, the rate of filtration (dV_{f}/dt) can be expressed as a function of pressure drop Dp by the modified D'Arcy's equation as (where A is the area of filtering surface, K is the D'Arcy's filter cake permeability and L is the thickness of the filter cake)

Filtration leaf test results indicate that the filtration rate of a protein product is 100 dry lbs/(ft^{2} hr). What size production filter would be required to obtain 100 dry lbs of filter cake/hr?