Filter Pressure Drop

Energy Efficiency and Pressure Drop

Air filters are basic components of air handling systems, and their life-cycle pressure drop significantly impacts a laboratory's energy consumption. Air filtration consumes energy in the way that conditioning coils do; however, the filters' energy consumption is greater because their resistance to air flow increases over time by definition. Specifying air filters with the lowest possible pressure drop nearly always pays for itself. Generally, the pressure drop is a direct function of the filtration efficiency; in other words, high-efficiency filtration results in a high pressure drop. When HEPA or ULPA filters are specified with only small reductions in pressure drop, significant energy savings can result from their long-term use. Filter media manufacturers have made great progress in developing low-pressure-drop media. Typically, specifying deeper filters reduces pressure drop and increases energy savings. For example, the average pressure drop at a face velocity of 100 feet per minute is between 0.35 and 0.40 inches w.g. for two-inch HEPA filters. A four-inch HEPA filter, which increases active media surface by 50 percent over a two-inch filter, lowers the pressure drop to between 0.25 and 0.35 in. w.g. A six-inch HEPA filter reduces the pressure drop to between 0.15 and 0.20 in. w.g. [McIlvaine et al., 1992; Lippold et al., 1990; NAFA Guide..., 1993; Kruse, 1991]

According to Lippold et al. (1990), the energy engineer should be aware of the following basic design requirements for pressure drop reductions:


High ratio of pleating


Pleat precision and uniformity

Thermal molding technology

Balancing filter cost and energy-efficiency

Optimizing final pressure drop: analysis method

HEPA filter pressure drop

Mini-pleat filter

Membrane filtration

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