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An understanding of gas-liquid two-phase interactions, aerosol particle deposition, and heat transfer is needed. Computational Fluid Dynamics (CFD) is becoming a powerful tool to predict aerosol behavior for related design work. In this study, FLUENT 6 is used to analyze the performance of aerosol sampling and concentration devices including inlet components (impactors), cyclones, and virtual impactors. The ω − k model was used to predict particle behavior in Inline Cone Impactor (ICI) and Jet-in-Well impactor (JIW). Simulation provided excellent agreement with experimental test results for a compact ICI. In the JIW, compound impaction is shown to cause the device to have a smaller cutpoint Stokes number than the single impaction unit. The size ratio of the well-to-jet was analyzed to find its influence on the total and side collections. Simulation is used to analyze liquid film, flow structure, particle collection, pressure drop, and heating requirements for a bioaerosol sampling cyclone. A volume of fluid model is used to predict water film in an earlier cyclone. A shell-volume is developed to simulate thin liquid film in large device. For the upgraded version cyclone, simulation is verified to successfully predict cutpoint and pressure drop. A narrowing-jet is shown to describe the flow evolution inside the axial flow cyclone. Turbulent heat transfer coefficients and surface temperatures are analyzed and heaters are designed for this cyclone. A double-outlet cyclone was designed and its pressure drop decreased about 25%, compared with a single-outlet cyclone. A scaled-down 100 L/min cyclone was also designed and tested based on the 1250 L/min unit. CFD is used to design a Circumferential Slot Virtual Impactor (CSVI) which is used for concentration of bioaerosol particles. Simulations showed a 3-D unstable flow inside an earlier version CSVI, which could explain acoustic noise and particle loss observed in the experiment. A smaller CSVI unit was designed using simulation and its flow was shown to be stable. CFD was then used to analyze the wake flow downstream of the posts to reduce particle losses and eliminate flow instabilities caused by wakes. A successful solution, moving the posts outside was developed by the use of CFD.

A modified wetted-wall cyclone using different methods of water injection techniques upstream of the inlet was designed as an improvement to a wetted-wall cyclone developed by White, which uses liquid injection through a port on the wall of the cyclone inlet. The new cyclone has a high aerosol sampling flow rate (1250 L/min) and maintains constant cut-point with the modified White-type cyclone along with greater collection efficiency, lower time response, and reduced pressure drop. The final air-blast atomizer cyclone (AAC2.1a) design considered has an aerosol-tohydrosol collection efficiency cut-point of 1.3 mm with collection efficiencies at 1 and 2 mm of 39.9% and 86%, respectively. The efficiency reported for the modified White-type cyclone for particle sizes of 1 and 2 mm was 40.5% and 76.3%, respectively, under no water bypass conditions. The aerosol-to-aerosol transmission efficiency for the AAC2.1a configuration was found to be approximately 53.7% for 1 mm diameter particles as compared with 67.2% for the modified White-type cyclone. Dry and wet time response tests were performed in which the modified White-type cyclone had an initial response of 2.5 minutes for a wet start and 1 minute for a dry start for a condition where there was no liquid carryover through the cyclone outlet. The rise time for AAC2.1a cyclone under dry and wet start conditions was 0.5 minutes and 1.3 minutes, respectively. The decay response of the modified White-type cyclone was 1.1 minutes for a wet start and 1.2 minutes for a dry start. The corresponding numbers for AAC2.1a cyclone were 1.4 minutes for a dry start and 1 minute for a wet start condition. Off design tests were run at approximately ±10% air flow rates to see the effect on cyclone performance. It was seen that at a 10% higher flow rate (1350 L/min) the efficiency was 54.3%. At a 10% lower flow rate (1125 L/min) the efficiency was 33.7% as compared with an efficiency of 39.9% at 1250 L/min for 1.0 mm PSL particles. It was found that at a water input of 0.8 mL/min the efficiency reduced to 79.3% as compared to 86% at an input flow rate of 1.6 mL/min for 2 mm size PSL.

Thesis (M.S.)--Naval Postgraduate School, 2002. / Thesis advisor(s): Russell L. Elsberry, Patrick A. Harr. Includes bibliographical references (p. 69). Also available online.

Sludge disposal is a worldwide problem due to increasing volumes and respective environmental regulations. Currently the most common ways to dispose sludge are agricultural use, disposal in landfills, incineration and sea dumping. By drying sludge volumes can be decreased and the respective heating value increased. Sludge mainly originates from wastewater treatment. The Swedish pulp and paper mills produce approximately 400 000 - 500 000 metric tons of dry sludge each year. This includes roughly 60 000 metric tons of dry biosludge which mainly consists of bacteria and is difficult to dry due to high amounts of intercellular water. New drying methods for biosludge are hence needed. The purpose of this project is to investigate the possibility to dry biosludge in a high-velocity cyclone dryer since the technology has been shown to be able to handle sticky materials. The sludge used in this project originates from the biological wastewater treatment at the pulp and paper mill Metsä Board Husum, located in Husum, Sweden. The achieved dry matter contents and the specific energy consumption have been examined and compared with established drying methods.  Design of experiments has been used during the trials for optimizing the information attained from a limited number of trials including effects of inlet air temperature, sludge feeding rate and recycling of drying air. The respective factors were varied in three steps and relevant temperature, pressure, humidity, flow and material mass values were measured for analysing the process.  Models for attained dry matter content, specific energy consumption (total and of the fan), removed water and fan power were developed and had high statistical significance. The models showed that sludge dry matter content up to 80% could be achieved. The total specific energy consumption was over 1.6 kWh/kg H2O, which is higher than for established drying methods, but the specific energy consumption of the fan was as low as 0.7 kWh/kg H2O. The specific energy consumption of the fan was used to approximate dryer operation with excess heat during which it could compete with all established drying methods. A case where the excess heat available at Metsä Board Husum would be used to dry generated biosludge was investigated and supported a need for a priority order between maximizing sludge dry matter content and minimizing specific energy consumption of sludge drying. If sludge dry matter content is prioritised alternative drying methods may prove more suitable. To attain a better understanding of the high-velocity cyclone dryer and drying of biosludge the evaporation energy of sludge at different dry matter contents, the effects of various sludge inflow temperatures and the effect of fan rotation speed should be included future investigations. / Bortskaffande av slam har blivit ett världstäckande problem på grund av stora volymer och miljöreglering. De vanligaste sätten att bortskaffa slam är genom markanvändning, deponering, förbränning och dumpning i haven. Genom att torka slammet minskar volymen och värmevärdet ökar. Slammet har sitt ursprung i vattenrenings processer och svenska pappers- och pappersmassabruk producerar ungefär 400 000 – 500 000 ton slam per år i torrvikt. Av dessa är ungefär 60 000 ton biologiskt slam som till största del består av bakterier och är svårtorkat på grund av den höga andelen intercellulärt vatten. För att torka biologiskt slam behövs nya torkmetoder och syftet med detta projekt vara att undersöka möjligheten att torka biologiskt slam i en cyklontork då cyklontorken kan hantera kladdiga material. Slammet som använts under projektet kommer från pappersbruket Metsä Board Husum. Torrhalten som kunde uppnås och den specifika energin har undersökt och jämförts med etablerade torkmetoder. Design of experiments användes för att optimera informationen som går att få ut från ett begränsat antal försök och påverkan av inluftstemperaturen, matningshastigheten av slammet och positionen av spjället i luftåtervinningssystemet har undersökts. Faktorerna varierades i tre steg och temperaturer, tryck, luftfuktigheter, flöden och vikter har mätts för att analysera processen.  Modeller för torrhalten, den specifika energin (totalt och för fläkten), avdrivet vatten och fläkteffekten har beräknats med hög statistisk signifikans. Modellerna visar att upp till 80 % torrhalt kan nås. Den totala specifika energin ligger över 1.6 kWh/kg H2O vilket är högre än den specifika energin för etablerade torkmetoder men den specifika energin för fläkten kan understiga 0.7 kWh/kg H2O. Den specifika energin för fläkten kan approximera att torken körs med överskottsvärme och det är fallet kan cyklontorken konkurer med de etablerade torkmetoderna. Möjligheten att använda sig av överskottsvärmen på pappersbruket Metsä Board Husum för att torka deras biologiska slam har undersökts och en prioritering mellan hög torrhalt och låg specifik energi kommer behöva göras. Om hög torrhalt prioriteras kan andra torkmetoder vara att föredra. För att öka förståelsen för cyklontorken och torkning av biologiskt slam kan förångningsenergin för slammet vid olika torrhalter, effekten på torkresultaten från olika temperaturer på slammet in i cyklonen och effekten av olika effekter på fläkten undersökas.

Thesis (M.S. in Meteorology)--Naval Postgraduate School, March 2005. / Thesis Advisor(s): Russell L. Elsberry. Includes bibliographical references (p. 103-105). Also available online.

Thesis (Ph. D.)--Ohio State University, 1997. / Includes bibliographical references (leaves 146-154).

Thesis (M.S.)--Florida State University, 2005. / Advisor: Dr. Robert Hart, Florida State University, College of Arts and Sciences, Dept. of Meteorology. Title and description from dissertation home page (viewed Sept. 19, 2005). Document formatted into pages; contains xiii, 99 pages. Includes bibliographical references.

This thesis contains an observational analysis of the genesis of Tropical Storm Allison (2001). Using a paradigm of tropical cyclone formation as the superposition of potential vorticity (PV) anomalies, the importance of different scales of PV merger to various aspects of Allison’s formation is discussed. While only the case of Allison is discussed in great detail, other studies have also documented PV superposition on various scales, and superposition could be important for most tropical cyclones. Preceding Allison’s genesis, PV superposition on the large scale destabilized the atmosphere and increased low-level cyclonic vorticity. This presented a more favorable environment for the formation of MCV-type PV anomalies and smaller, surface-based, meso-β-scale vortices. Although these vortices eventually merged to form a more concentrated vortex with stronger surface pressure gradients, the merger happened well after landfall of Allison and no strengthening ensued. The unstable, vorticity-rich environment was also favorable for the development of even smaller, meso-γ-scale vortices that accompanied deep convective cells within one of Allison’s meso-β-scale vortices. The observations herein suggest that the meso-γ- scale convective cells and vortices are the respective source of PV production and building blocks for the meso-β-scale vortices. Finally, this thesis discusses issues related to the multiple vortex nature of tropical cyclone formation. For instance, the tracking of developing tropical cyclones is greatly complicated by the presence of multiple vortices. For these cases, the paradigm of a single cyclone center is inappropriate and alternative tracking methods are introduced.

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