The relationship between filter pressure drop, indoor air quality, and energy consumption in rooftop HVAC units

Estimates of HVAC filtration efficiency for fine and ultrafine particles of outdoor origin

“…Two different scenarios of outdoor PM 2.5 mass concentrations for each outdoor PSD were estimated using two different assumptions for particle density. First, we assumed spherical particles with constant unit density (1 g/cm 3 ) for all particles, both for simplicity and to reflect previous assumptions in the literature (El Orch et al, 2014;Riley et al, 2002;Waring and Siegel, 2008;Zaatari et al, 2014). Second, we assumed spherical particles with density varying with diameter according to the average of that reported during two experimental campaigns in two German cities (Neusüss et al, 2002): 1.3 g/cm 3 for D p < 140 nm; 1.4 g/cm 3 for 140 nm D p < 420 nm; 1.5 g/cm 3 for 420 nm D p < 1.2 mm; 1.6 g/cm 3 for 1.2 mm D p < 3.5 mm; and 1.7 g/cm 3 for 3.5 mm D p < 10 mm.…”

“…PM 2.5 mass removal efficiency will vary highly depending on particle size distribution (PSD) and particle density (El Orch et al, 2014;Hanley et al, 1994;Riley et al, 2002). Although one recent study found strong correlations between E 1 removal efficiency and indoor and outdoor origin PM 2.5 mass removal efficiency (Zaatari et al, 2014), it was limited by a small number of outdoor PSDs and PM 2.5 mass concentrations. A larger number of outdoor PSDs is important to capture because they can vary widely by location (e.g., rural, urban, and close to traffic), season (e.g., winter, spring, summer, and fall), or even time of day (e.g., morning, afternoon, and nights) (Costabile et al, 2009;Jaenicke, 1993;Kelly et al, 2011;Puustinen et al, 2007;Seinfeld and Pandis, 2006;Virtanen et al, 2006).…”

“…This is because outdoor particles can penetrate indoors (Chen and Zhao, 2011) and people in industrialized countries spend much of their time indoors (Jenkins et al, 1992;Klepeis et al, 2001). Indoor particle control technologies such as stand-alone air cleaners and particle filters installed in central heating, ventilating, and air-conditioning (HVAC) systems are being increasingly relied upon to reduce indoor concentrations of particles of both indoor and outdoor origin (Brown et al, 2014;Howard-Reed et al, 2003;MacIntosh et al, 2010MacIntosh et al, , 2008Offermann et al, 1985;Riley et al, 2002;Siegel, 2012a, 2013;Wallace et al, 2013Wallace et al, , 2004Zaatari et al, 2014).…”

Evaluating the Sensitivity of the Mass-Based Particle Removal Calculations for HVAC Filters in ISO 16890 to Assumptions for Aerosol Distributions

“…The use of volume distributions necessitates an underlying assumption of spherical particles and constant unit density for volume-based removal efficiencies that yields an equivalent to mass-based removal efficiencies. While these assumptions are not always valid [22][23][24], they are widely used assumptions [25][26][27][28] that have been shown to have only a minimal impact on estimates of mass-based removal efficiency for HVAC filters [29]. Next, filters that are designed to filter primarily PM 1 and PM 2.5 size fractions are assumed to be characterized using the urban volume distribution function, while filters designed to filter primarily PM 10 are assumed to be characterized using the rural volume distribution function.…”

Green, Clean, & Mean: Pushing the Energy Envelope in Tech Industry Buildings

“…Pacific Northwest in winter time). (Zaatari et al, 2014). This data shows a wide variety of pressure drops owning to differences in filter design.…”