where
PT = total pressure loss, horsepower per 1000 acfm
PG = contacting power based on gas stream input, horsepower per 1000 acfm
Δp = pressure drop across the scrubber, inches H2O
PL = contacting power based on liquid stream energy input, horsepower per 1000 acfm
pL = liquid inlet pressure, pounds per square inch
QL = liquid feed rate, gallons per minute
QG = gas flow rate, cubic feet per minute
The scrubber collection efficiency is also expressed as the number of transfer units: