This study is aimed at developing modeling methodologies for simulating the flow of air and aerosol particles through fibrous filter media made up of micro- or nano-fibers. The study also deals with modeling particle deposition (due to Brownian diffusion, interception, and inertial impaction) and particle cake formation, on or inside fibrous filters. By computing the air flow field and the trajectory of airborne particles in 3-D virtual geometries that resemble the internal microstructure of fibrous filter media, pressure drop and collection efficiency of micro- or nano-fiber filters are simulated and compared with the available experimental studies. It was demonstrated that the simulations conducted in 3-D disordered fibrous domains, unlike previously reported 2-D cell-model simulations, do not need any empirical correction factors to closely predict experimental observations. This study also reports on the importance of fibers’ cross-sectional shape for filters operating in slip (nano-fiber filters) and no-slip (micro-fiber filters) flow regimes. In particular, it was found that the more streamlined the fiber geometry, the lower the fiber drag caused by a nanofiber relative to that generated by its micron-sized counterpart. This work also presents a methodology for simulating pressure drop and collection efficiency of a filter medium during instantaneous particle loading using the Fluent CFD code, enhanced by using a series of in-house subroutines. These subroutines are developed to allow one to track particles of different sizes, and simulate the formation of 2-D and 3-D dendrite particle deposits in the presence of aerodynamic slip on the surface of the fibers. The deposition of particles on a fiber and the previously deposited particles is made possible by developing additional subroutines, which mark the cells located at the deposition sites and modify their properties to so that they resemble solid or porous particles. Our unsteady-state simulations, in qualitative agreement with the experimental observations reported in the literature, predict the rate of increase of pressure drop and collection efficiency of a filter medium as a function of the mass of the loaded particles.

Devices for converting solar energy to electrical energy are not considerably efficient, though there are abundant renewable solar energy sources. Therefore there is a continuous call for investigation of new devices that are efficient and eco-friendly thereby contributing to harvested energy technology. This thesis characterizes the optical constant (refractive index) of a novel material, cobalt oxide-antimony doped tin oxide (CoO-ATO). Thin film of CoO-ATO is generated using spin coating of CoO-ATO solution having 76.33% chloroform, 13.47% polystyrene, 10% antimony doped tin oxide and 0.2% cobalt oxide by weight. The thin film is analyzed through ellipsometry to acquire the refractive index of the material through the visible spectrum, which is used for modeling an antireflective coating in a solar cell. The model is designed and analyzed by simulation using computer simulated technology, and the results of the analysis of a thin film or a nanofiber membrane of the novel material implemented as an antireflective coating layer that affects the absorption efficiency of the optoelectronic device. The result of the analysis showed enhancement of absorption efficiency within the visible spectrum for both thin film and nanofiber membrane of the novel material CoO-ATO. The absorption through thin film was more than that of the nanofiber membrane.

It was found that a significant improvement of mechanical properties of CFRPs can be achieved by the adjustment of the matrix properties such as toughness and CF/matrix adhesion via the chemical modification, as well as the physical modification by a small amount of cheap and environment-friendly nano fibers. Based on investigation of fracture mechanisms at macro/micro scale, the effects of matrix properties and nano fiber on the mechanical properties of CFRP have been discussed. Subsequently, the relationship has been characterized by a numerical model to show how to modulate the parameters of the matrix properties to achieve excellent fatigue properties of CFRP. / 博士(工学) / Doctor of Philosophy in Engineering / 同志社大学 / Doshisha University