Ryan Mead-Hunter

Plateau Rayleigh instability simulation.

The well-known phenomena of Plateau-Rayleigh instability has been simulated using computational fluid dynamics (CFD). The breakup of a liquid film into an array of droplets on a cylindrical element was simulated using a volume-of-fluid (VOF) solver and compared to experimental observations and existing theory. It is demonstrated that the VOF method can correctly predict the breakup of thins films into an array of either axisymmetric droplets or clam-shell droplets, depending on the surface energy. The existence of unrealistically large films is precluded. Droplet spacing was found to show reasonable agreement with theory. Droplet motion and displacement under fluid flow was also examined and compared to that in previous studies. It was found that the presence of air flow around the droplet does not influence the stable film thickness; however, it reduces the time required for droplet formation. Novel relationships for droplet displacement were derived from the results.

Impacts of household coal and biomass combustion on indoor and ambient air quality in China: Current status and implication.

This review briefly introduces current status of indoor and ambient air pollution originating from household coal and biomass combustion in mainland China. Owing to low combustion efficiency, emissions of CO, PM2.5, black carbon (BC), and polycyclic aromatic hydrocarbons have significant adverse consequences for indoor and ambient air qualities, resulting in relative contributions of more than one-third in all anthropogenic emissions. Their contributions are higher in less economically developed regions, such as Guizhou (61% PM2.5, 80% BC), than that in more developed regions, such as Shanghai (4% PM2.5, 17% BC). Chimneys can reduce ~80% indoor PM2.5 level when burning dirty solid fuels, such as plant materials. Due to spending more time near stoves, housewives suffer much more (~2 times) PM2.5 than the adult men, especially in winter in northern China (~4 times). Improvement of stove combustion/thermal efficiencies and solid fuel quality are the two essential methods to reduce pollutant emissions. PM2.5 and BC emission factors (EFs) have been identified to increase with volatile matter content in traditional stove combustion. EFs of dirty fuels are two orders higher than that of clean ones. Switching to clean ones, such as semi-coke briquette, was identified to be a feasible path for reducing >90% PM2.5 and BC emissions. Otherwise, improvement of thermal and combustion efficiencies by using under-fire technology can reduce ~50% CO2, 87% NH3, and 80% PM2.5 and BC emissions regardless of volatile matter content in solid fuel. However, there are still some knowledge gaps, such as, inventory for the temporal impact of household combustion on air quality, statistic data for deployed clean solid fuels and advanced stoves, and the effect of socioeconomic development. Additionally, further technology research for reducing air pollution emissions is urgently needed, especially low cost and clean stove when burning any type of solid fuel. Furthermore, emission-abatement oriented policy should base on sound scientific evidence to significantly reduce pollutant emissions.

Sliding/Rolling Phobic Droplets along a Fiber: Measurement of Interfacial Forces

Phobic droplet-fiber systems possess complex geometries, which have made full characterization of such systems difficult. This work has used atomic force microscopy (AFM) to measure droplet-fiber forces for oil droplets on oleophobic fibers over a range of fiber diameters. The work adapted a previous method and a theoretical model developed by the authors for philic droplet-fiber systems. A Bayesian statistical model was also used to account for the influence of surface roughness on the droplet-fiber force. In general, it has been found that the force required to move a liquid droplet along an oleophobic filter fiber will be less than that required to move a droplet along an oleophilic fiber. However, because of the effects of pinning and/or wetting behavior, this difference may be less than would otherwise be expected. Droplets with a greater contact angle (~110°) were observed to roll along the fiber, whereas droplets with a lesser contact angle (<90°) would slide.

Evaluation of the Force Required to Move a Coalesced Liquid Droplet along a Fiber

This work presents a theoretical model describing the force required to move a coalesced liquid droplet along an oleophilic filter fiber. Measurements have been made using the atomic force microscope (AFM) to examine these forces over a range of fiber and droplet diameters as well as oil properties. Good agreement between measured and modeled forces was found. The influence of droplet displacement perpendicular to the fiber on the force required to move the droplet has also been determined experimentally and theoretically. It was found that fiber surface inhomogeneities are likely to influence results. This work has also established empirical relationships that can be used to predict the force, based on a known droplet volume, for the liquid types used.

Biodiesel exhaust–induced cytotoxicity and proinflammatory mediator production in human airway epithelial cells

Increasing use of biodiesel has prompted research into the potential health effects of biodiesel exhaust exposure. Few studies directly compare the health consequences of mineral diesel, biodiesel, or blend exhaust exposures. Here, we exposed human epithelial cell cultures to diluted exhaust generated by the combustion of Australian ultralow‐sulfur‐diesel (ULSD), unprocessed canola oil, 100% canola biodiesel (B100), and a blend of 20% canola biodiesel mixed with 80% ULSD. The physicochemical characteristics of the exhaust were assessed and we compared cellular viability, apoptosis, and levels of interleukin (IL)‐6, IL‐8, and Regulated on Activation, Normal T cell Expressed and Secreted (RANTES) in exposed cultured cells. Different fuel types produced significantly different amounts of exhaust gases and different particle characteristics. All exposures resulted in significant apoptosis and loss of viability when compared with control, with an increasing proportion of biodiesel being correlated with a decrease in viability. In most cases, exposure to exhaust resulted in an increase in mediator production, with the greatest increases most often in response to B100. Exposure to pure canola oil (PCO) exhaust did not increase mediator production, but resulted in a significant decrease in IL‐8 and RANTES in some cases. Our results show that canola biodiesel exhaust exposure elicits inflammation and reduces viability of human epithelial cell cultures in vitro when compared with ULSD exhaust exposure. This may be related to an increase in particle surface area and number in B100 exhaust when compared with ULSD exhaust. Exposure to PCO exhaust elicited the greatest loss of cellular viability, but virtually no inflammatory response, likely due to an overall increase in average particle size.

Route of exposure alters inflammation and lung function responses to diesel exhaust

Abstract Context: Mice are commonly used in studies investigating the effects of diesel exhaust exposure on respiratory health. A plethora of studies in this field has resulted in a range of exposure protocols, from inhalation of diesel exhaust, to the administration (via various routes) of diesel exhaust particles in solution. Objective: In this study, we compared the physiological consequences of short-term exposure to diesel exhaust via inhalation to those due to exposure to the same diesel exhaust particles suspended in solution and delivered intranasally. Materials and methods: Adult BALB/c mice were exposed to diesel exhaust via inhalation for 2 hours per day for 8 days. A representative, simultaneous sample of particles was collected and a second group of mice then exposed to them suspended in saline. A low and a high-dose were studied, with these matched based on respiratory parameters. Six and twenty-four hours after the last exposure we measured bronchoalveolar inflammation, lung volume, lung function and the amount of elemental carbon in alveolar macrophages. Results: Exposure via either route elicited pulmonary inflammation and changes in lung function. We identified significant differences in response between the two routes of exposure, with mice exposed via inhalation generally displaying more realistic dose-response relationships. Mice exposed via intranasal instillation responded more variably, with little influence of dose. Conclusions: Our results suggest that selection of the route of exposure is of critical importance in studies such as this. Further, inhalation exposure, while more methodologically difficult, resulted in responses more akin to those seen in humans.

Knitted fibrous filter media

Abstract Knitted fibrous filter media represent a special class of filter media, which tend to be utilized for industrial applications, usually related to mist separation in process industries. These filters are advantageous for many applications, as their knitted structure imparts significant mechanical strength—similar to woven filters, without the high packing density of most woven filters. In this chapter, we discuss advantages and disadvantages of knitted fibrous filter media in comparison to felted (nonwoven) and woven media. An overview of industrial applications is presented, plus a summary of studies related to pressure drop and efficiency and research specific to knitted mist eliminator media. Suggestions for further research are also provided.

Fibrous filtration of liquid aerosols

Abstract Fibrous filters and mist eliminators are widely used in a range of manufacturing and process industries to remove liquid mists from gas streams, thereby coalescing them to recover the bulk liquid and prevent emissions. The range of applications is very broad, including compressed gas cleaning, engine crankcase ventilation, (liquefied) natural gas, propane (LPG) and hydrocarbon production and processing, cooling towers, machining and cutting processes. Although research on mist filtration has been increasing since the late 1950s, and some of the fundamental physico-chemical processes were described as early as 1870, the scientific questions in the field are far from resolved. This is largely due to the complex kinetics of gas and fluid phases, and the wide range of possible filter geometric properties and surface energy. However, over the last 15 years, significant progress has been made in the field. This chapter presents the state of current research, comparing currently available models for capture, saturation, and pressure drop and discussing their applicability. Key gaps in the literature and necessary directions for future study are also given.

Occupational exposures to agricultural dust by Western Australian wheat-belt farmers during seeding operations

Abstract Agricultural operations routinely expose farm workers to high levels of soil dust and other airborne particulate matter that have been linked to adverse health outcomes. The main objective of this study was to investigate exposure to agricultural dust during seeding operations of Western Australian farm workers. Twenty-one wheat-belt farms were recruited to participate in the study. Data were collected over the 6-week seeding period of April–June 2014. Each farm was visited once, and workers were asked to complete a workplace survey that asked questions related to minimizing exposure to agricultural dusts and occupational health and safety issues on their farm. Farmers were also asked to simultaneously participate in monitoring of personal exposure to inhalable or respirable dust along with real-time monitoring for particulate air pollution in their tractor cabin. Sampling was undertaken for 4 hr. The results showed that, on average, Western Australian farmers were exposed to personal respirable dust concentrations above the Australian Institute of Occupational Hygienists recommended guideline values, with some farmers being exposed to concentrations up to seven times higher than the value for respirable dusts. In comparison, in-cabin dust concentrations were lower, although some individual tractors recorded intermittently higher levels, which might be attributed to the type of work activity or process being undertaken. Remaining in tractor cabins with closed doors and windows with properly maintained seals might minimize the infiltration of hazardous dusts and may provide some protection from dust exposures. Future research should focus on educating and providing farm owners and workers with more information on adopting work processes and procedures related to minimizing harmful exposures to agricultural dusts.

Comment on “Regional particle size dependent deposition of inhaled aerosols in rats and mice” by Kuehl et al.

Kuehl et al. (2012) recently produced an excellent paper on regional polydisperse aerosol deposition in rats and mice, comparing their results with earlier work by Raabe et al. (1988). Kuehl et al. (2012) concluded that the differences between the results were most likely because the Raabe et al. (1988) study used monodisperse particles, while the former used polydisperse particles (possible differences in breathing rates and differing mouse strains were also suggested). However, the particle densities used in both studies differed significantly. Raabe et al. (1988) used silica particles and reported a density ( p) of 2460 kgm , however most literature gives a higher density of 2700 kgm . Furthermore the particles were labelled with Yb, with a reported density of 7000 kgm . Kuehl et al. (2012) do not report the density of the particles they used, however given that they were generated from a colloidal sulphur in a weak saline solution and apparently not explicitly dried using a diffusion dryer or similar, it is reasonable to assume that their particles have an effective bulk density of 1000 kgm . This assumption is supported by our simulated deposition study (Mead-Hunter et al., 2013) which produced results which agreed well with Kuehl et al.’s (2012) results, using either 0.5mm polydisperse or monodisperse particles with p1⁄4 1000 kgm . Therefore, in addition to the fact that one particle type was a (dry) solid and one a liquid colloid, a significant physical size difference exists between the particles used in the Raabe et al. (1988) and Kuehl et al. (2012) studies. Particle capture by inertial mechanisms can be assumed to be dependent on mass mean aerodynamic diameter (MMAD), or more precisely on Stokes’ number (Stk). For equivalent flow velocities and deposition surface geometries, we can simplify stokes number to be proportional to,