Development of a New Laboratory Test Methodology for Rapid Ageing of HVAC Filters with a Representative Urban Aerosol Mass Size Distribution at High Concentration
CHUNXU HUANG, Iane Gomes, Laura Ajala, Elliot Cram, Ta-Kuan Chuang, Nusrat Jung, Brandon E. Boor,
Purdue University Abstract Number: 267
Working Group: Control and Mitigation Technology
AbstractAir filters installed in residential and commercial HVAC systems encounter a complex mixture of aerosols of outdoor and indoor origin during their service life. Standardized laboratory test methodologies are important for evaluating the loading behavior of HVAC filters. Loading aerosols commonly used to age HVAC filters include various test dusts (ISO-12103-1-A2, ISO-12103-1-A4, ASHRAE Test Dust) that are primarily composed of coarse mode particles (1 to 100 µm). However, urban aerosol mass size distributions often feature a prominent accumulation mode between 0.1 and 1 µm that is not well represented by traditional loading aerosols. The aim of this study is to develop a new laboratory test methodology for rapid ageing of HVAC filters with a representative urban aerosol mass size distribution at a high concentration to better predict long-term changes in HVAC filter performance. A HVAC filter test rig was custom designed and built following ASHRAE 52.2 specifications to artificially age HVAC filters with sub-micron potassium chloride (KCl) aerosol produced by a thermal aerosol generator. The KCl aerosol is formed by burning KCl sticks in a high temperature oxygen-propane flame and is delivered to the test rig via a damper-controlled intake duct. The loading behavior of a collection of air filters of variable design and efficiency (pleated MERV8, electrostatic bag MERV13, V-cell MERV14) was evaluated using the new experimental protocol. KCl aerosol size distributions were measured across the test filter using a scanning mobility particle sizer (SMPS) and a high-resolution electrical low pressure impactor (HR-ELPI+). Artificial ageing experiments were conducted until the filter pressure drop reached 1.5 in. H
2O. The new test methodology successfully aged MERV8, MERV13, and MERV14 filters to 1.5 in. H
2O in several hours. Loading curves were sensitive to the MERV rating, volumetric airflow rate, relative humidity, and KCl stick feed rate. The results demonstrate that the new sub-micron KCl loading aerosol is a time- and cost-effective technique to artificially age HVAC filters with a particle mass size distribution representative of that found in HVAC installations in buildings.