Rozprawa habilitacyjna-- Warsaw. / Bibliography: p. 83-[84].

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Supervisor: Michael D. Bryant. Vita. Includes bibliographical references. Also available from UMI.

published_or_final_version / Dentistry / Master / Master of Dental Surgery

 Drying process needs lots of energy and usually prone to high equipment and operational cost. Research tasks have focused on improving the drying performance and reducing the energy consumption rate. Among a number of industries, textile manufacturing needs the process intensively. It is surprising that little research has concerned principle enhancement and drying process design. In the support by Fong’s National Engineering Company Limited, a series of research that targeting to the inadequacy of technology development for machinery and process design have been conducted. The redevelopment of machinery design has based upon a heat setting machine –ECO dryer. The machine was used as a working platform to supply all necessary testing information before and after the enhancement. The ductwork and air distribution system design have been revised to improve the unevenness drying problems appeared in the heat setting of fabrics. Two main research scopes have been performed that included the development of a new duct sizing approach –Uniform Jet Velocity (UJV) and redesigning the air chambers. The proposed UJV approach is a new air duct design model developed from fluid dynamics principles. The air jet speed along each nozzle is maintained at a constant rate to provide a uniform jet impingement effect. A duct size algorithm was proposed to adjust the cross sectional area ratio between the main and branch streams for the target of producing a constant impingement velocity across the entire air duct. In the enhancement of the air distribution system design, Computational Fluid Dynamics (CFD) analytical approaches were used to model air flow patterns before and after the redesign of air chambers. The CFD analysis results told that a linear air distribution system with four sub-chamber design could produce the best air distribution pattern on the ECO dryer. The request of an accurate drying cycle time predication is also large in textile industry. It is because the problems of under-and over-drying usually happen in the jet impingement process. The second essential objective in the research is to develop systematical approaches for a good qualifying of a drying cycle. Four analytical models have been studied that included First order kinetics, Diffusion, model based on solutions of diffusion equation and Wet surface. An equation for each of the models was developed to describe the characteristics of a porous type fabric drying process. In the study, the required modeling parameters were empirically determined, and the accuracy among the models has been compared. Findings from the research have proved that the model based on solutions of diffusion equation can be the best strategy in presenting a drying cycle under different machine settings. The investigation has not ceased after the completion of the hot air jet impingement research. The study objectives have moved onto an alternative drying technology using steam as the drying medium. Due to many problems reported in the drying of yarn packages using electro-magnetic waves, moist heat drying technology is urgently needed. At the final part of the research, two CFD simulation models namely constant viscous resistance and increasing viscous resistance were studied. A preliminary result generated from ANSYS CFD analysis results was obtained that has opened up a new study area for further elaboration of a new drying technology, and hopefully can be practically applied to textile industry in the near future. / published_or_final_version / Mechanical Engineering / Master / Master of Philosophy

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A need exists for developing a drying technique for heat-sensitive materials as the conventional heat-based drying methods often produce changes in their physico-chemical properties. This thesis presents a non-thermal electrohydrodynamic (EHD) drying technique that may be used to dry both heat-sensitive and viscous materials. A single point-to-plate EHD system was used in de-watering sugar solutions and glycerin-water mixtures having viscosity between 2 and 22 mPa s. The EHD and forced air (2.5 m s-1) each produced 3 to 5 times higher evaporation rate than the control, which was at ambient temperature and relative humidity. The vapor flux decreased considerably and quadratically compared with the control as viscosity increased, and the dehydration kinetics was linear regardless of viscosity. Agar gels showed a linear relationship between vapor flux and time, and EHD was effective in drying at sub-zero temperatures. The agar temperature during drying was significantly below the ambient, indicating evaporative and entropic cooling.

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As a result of the current interest in theories designed to explain the processes whereby precipitation originates in clouds and, if possible, to devise methods of causing or initiating precipitation at times or places more desirable than those chosen by Nature, and particularly in view of certain assumptions made in the formulation of some of these theories, experiments are in progress to study the behaviour of water particles in a region of moist air and small water droplets such as is found in a cloud. For such experiments, some means of producing a cloud, preferably of controlled characteristics, in the laboratory is needed.