Application of Microfibrous Materials in Air Filtration for Improving Indoor Air Quality

Abstract

The growing emphasis on indoor air quality has resulted in the need for more stringent air filtration requirements in heating, ventilation, and air conditioning (HVAC) systems. The typical filtration system consists of a pre-filter for removing coarse particles, a high-efficiency particulate air (HEPA) filter for removing fine particles, and a separate adsorptive system for removing molecular contaminants as necessary. However, the design of current filtration systems has two major drawbacks: the more space requirement caused by three filtration units and the high energy consumption. The studies described in this dissertation focused primarily on the development of an innovative dual-functional filtration unit that can simultaneously remove both particulate and molecular contaminants with significantly low energy cost. The dual-functional filtration unit used a class of special filter media known as microfibrous materials (MFM) that are made of sorbent/catalyst particles immobilized within sinter-locked three-dimensional matrices of microfibers, and employed a special filter packing design known as multi-element structured arrays (MESA). The studies of the design and optimization of pleated MFM filters and MFM MESA units were conducted by applying two previously developed semi-empirical pressure drop models. The results demonstrated that the design parameters have dramatic impact upon initial pressure drop across single MFM pleated filters and MFM MESA units. A comparison in a performance index of carbon loading capacity divided by initial pressure drop at 500 fpm between the optimal MFM MESA unit and a commercially available honeycomb carbon filter (HCF) has revealed a substantial improvement of the optimal MFM MESA unit. In addition, the experimental results on single HCF, V-shaped HCF MESA unit and W-shaped HCF MESA unit further confirmed the significant benefits of the MESA design. Therefore, it can be used as a platform for commercially available filters with high resistance. The impact of design parameters on the initial pressure drop across various MESA units that contained commercially available pleated filters for particle removal was experimentally investigated. A comparison of energy consumption between a single pleated filter and a V-shaped MESA unit indicated that the MESA design has the great potential for increasing the energy efficiency and saving the cost in HVAC systems. To better understand the dust loading behavior for extending the filter service life, the pressure drop evolution of pleated filters subjected to polydiserpsed particles was studied. An empirical model was proposed to predict the pressure drop of pleated filter during the dust loading process. The agreement between the dust loading experimental results and the model results demonstrated that the developed empirical model can accurately predict the pressure drop during the dust loading process. The present studies provided insights into novel approaches for improving and enhancing the filtration performance of future media and filter designs.