

:: Section 7Pressure Drop and Power
Since impaction relies on the flow velocity, a higher efficiency is the result of a higher flow velocity. However, a higher flow velocity is accompanied by a higher pressure drop across the system that can be translated into cost as a more powerful fan is required. The pressure drop can be determined by: where ρ_{g} is density of gas and N_{H} is number of gas inlet velocity head. The pressure drop for a general purpose, a medium efficiency or a high efficiency cyclone is typically 24, 48 and 810 inch H_{2}O, respectively. The power requirement (W_{f}) can then be determined according to: The total cost is related to the power as
where TC is total cost and $ is unit electricity cost. 