FILTER PERFORMANCE UNDER SIMULATED REAL-WORLD CONDITIONS

FILTER PERFORMANCE UNDER SIMULATED REAL-WORLD CONDITIONS By Qiang Wang, M.S. A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at Virginia Commonwealth University. Virginia Commonwealth University, 2016 Major Director: Dr. Da-Ren Chen Professor and Floyd D. Gottwald, Sr. Chair in Mechanical and Nuclear Engineering Evaluating the performance of filter media for filtration application is essential to assure design engineers and users that the filter device will deliver promised performance for specific applications under the environmental stress. The study of particle loading characteristics of a filter medium in the laboratory setting is typically performed under the steady-state conditions, i.e., at the constant particle concentration and flow rate through filter media during the entire process. In reality, filtration products are normally operated under the situations that either the flow rate or mass concentration of particles passing through media is varied in time. The success of translating the data collected in the laboratory setting to predict the performance of filter media in the field is thus very limited. In order to bridge the gap between the laboratory testing and real-world performance of filter media, it is xiii necessary to investigate the performance of filter media under the real-world conditions, i.e., unsteady flow rate or mass concentration. Particulate Respirator filters have been widely utilized in industrial and daily life to protect individuals from inhaling harmful particles. New filter media for respirator applications continuously are in high demand to meet various challenges in personal particulate matter (PM) protection. The US National Institute for Occupational Safety and Health (US NIOSH) certificates particulate respirators in accordance with Title 42 Code of Federal Regulations (CFR) Part 84. This standard testing is only operated under constant flow conditions. To better understand the performance of respirator filter media in real-world applications, it is thus necessary to evaluate the performance of filter media under realistic flow conditions such as simulated human breathing. A new advanced testing setup will be introduced and applied to systematically investigate the performance of various respirator filters under cyclic flow. In addition, a flat filter testing apparatus was built, which is capable of adjusting the testing flowrate (or face velocity) and particle mass concentration under the controlled patterns. HVAC entrance filter panels are widely used in aircraft to maintain proper air quality in the passenger cabin, but it has been reported that HVAC filter panels are often not-well utilized in practical circumstances. The non-uniform particle deposition pattern on HVAC filter panels was diagnosed be the most possible reason reducing the lifetime of HVAC filter panels, and normally only partial area on the filter panel were effectively utilized. A typical HVAC system takes up a rather large space which is impossible to meet based on school xiv laboratory conditions, as well as the actual layout in the cargo area of aircraft. Thus, numerical modeling and simulation would be an alternate method to deal with this problem instead of experiments. Computational fluid dynamics (CFD), is applying numerical methods and algorithms to solve and analyze problems; it is primarily employed to study the performance of pleated HVAC filter media under non-uniform particle loading in this study. The overall goals of this research are (1) to study the performance of filter media under unsteady conditions (i.e., the performance of respirator filter media under simulated breathing conditions); and (2) to investigate the issue of particle non-uniform deposition on HVAC filter panels. A new experimental setup was developed to accomplish the former goal. The numerical modeling tool, Computational fluid dynamics (CFD), was applied to achieve the latter objective.