Filtration performance of innovative fibrous media

Air filtration using fibrous air filters is a common solution used in HVAC (Heating, Ventilation Air conditioning) systems for reducing particle matter contamination inside the building. An indoor environment with strict particle control at different levels is required by several applications. The filtration performance of air filters is a characterizing factor for its use. It includes airflow resistance, particle removal efficiency, and service life. These factors impact energy, cost, functionality, and life cycle aspects. The filtration performance of air filters can be tested on the product or the material level as flat sheet fibrous filter media. This latter approach is considered the main purpose of this study. Ideally, high efficiency and low air resistance are needed for better-quality fibrous filter media. The filtration performance of fibrous filter media can be improved by optimizing the filtration characteristics of fibers, which include fiber size, solid volume fraction, thickness, and charges. Electrospinning technology allows the production of fibers on a nanometer scale. Theoretically, finer fibers increase air resistance by maximizing particle removal efficiency at a finer particle size range. Increasing pressure drop can be compensated partially by the slip effect as fiber diameters approach the mean free path of air molecules; this provides a better tradeoff between efficiency and air resistance. Standardized experimental tests are an effective way of investigating the real behavior of such filter media, providing reliable results with good accuracy. Electrospun nanofiber media as PAN (Polyacrylonitrile), PANCO (Polyacrylonitrile + Caster oil), PAN15CNC (Polyacrylonitrile + Caster oil + Cellulose nanocrystals), PANCO15CNC (Polyacrylonitrile + Castor oil + Cellulose nanocrystals), PAN0.4CNF (Polyacrylonitrile + Cellulose nanofibrils) and PANCO0.4CNF (Polyacrylonitrile + Caster oil + Cellulose nanofibrils), are firstly tested on air resistance and efficiency of clean media. The airflow resistance of clean samples is tested at different filtration velocities, from 0.01m/s to 0.15m/s. Fractional particle removal efficiency at fixed filtration velocity 0.1m/s is then measured using two types of optical particle counters with different measuring particle size ranges, i.e., 0.3μm to 10μm and 90nm to 7.5μm, respectively. A wider detecting range is essential for studying nanofiber samples' most penetrating particle size (MPPS) and minimum efficiency. The second part is studying the loading behavior of several types of filter media using two types of test machines. One is the standardized mask test machine TSI 8130A compared to another test rig with relative humidity and temperature control. Loading test enabling assessment of service life of fibrous filter media. First tests are performed on TSI 8130A, using neutralized ultrafine NaCl solid particles to charge filter media at a fixed flow rate. Particle size distribution from the aerosol generator is studied using a scanning mobility particle sizer whose detecting range is from 10nm to 1000nm. Relative humidity is monitored during tests as it impacts the loading behavior of filter media. The following tests are performed on the test rig with relative humidity control for the preliminary characterization of the working status of machine components. Studies on aerosol atomizers and neutralizers are performed to find technical solutions for the reliable results of loading tests on the test rig.