(293c) Design Characteristics Of Pleated Filters And Their Corresponding Effect On Pressure Resistance
Pressure resistance plays a fundamental role in determining air handler specifications and is a key component in determining the energy needed to flow air through the system. Pressure drop within a HVAC system is created by a combination of resistances such as flow in the duct, around bends, across baffles, and through filtering elements. Numerous filtration systems are commercial available; however, pleated filters are one of the more common styles. To increase the available filtration area, a pleated filter uses a highly folded media. The additional area reduces the air velocity through the media, thus reducing the pressure drop across the filter. The extra media also extends the filter's useful life. If the pressure drop across a pleat filter can accurately be predicted, then the system's energy consumption and removal efficiency can be optimized.
For a pleated filter, the pressure resistance curve possesses a ?U? shaped curve when plotted against the pleat count. At low pleat counts, the primary contributor to total pressure drop is the resistance in the media. As the pleat count increases, the resistance due to the media decreases; however, the viscous resistances begin to rise. Thus, each pleated filter passes through an optimal pleat count corresponding to the minimal pressure drop.
This study's objectives are to identify the design parameters and assess their consequential pressure drops. The research proposes a model capable of making accurate predictions of the pressure drop across a pleated filter based solely on physical properties of the media. The design parameters are determined as follows: filter dimensions (height, width, and depth), media type (thickness and permeability), filter housing, and pleat count. An empirical model is created by systematically altering the filter's parameters and observing the resulting pressure changes. Experimental data is collected from twenty filters with various media types, filter depth, and pleat counts. The data is utilized in conjunction with Darcy's law, Bernoulli's equation, and the equation of continuity to model the filter as a series of individual resistances.