Coulomb drag-induced ion current flow is reported, achieved through coupling of electronic charge carriers along the lattice of a narrow single-walled carbon nanotube to electrolytic charge within the confines of the nanotube. Solid-state electrical contacts to the nanotube induce ion transport through it in the absence of an axial electric field; in the presence of such a field, the device behaves as an n-type ionic transistor. Ionic currents as high as 1nA have been recorded without alternate driving forces. Asymmetric functionalization of single walled carbon nanotube end groups further enhances the rectifying behavior of the device, yielding a current rectification ratio as high as 10 at moderate axial field strengths. By achieving ion pumping through a solid-state electrical input, the system offers promising solutions to nanoscale applications including purification, drug delivery, and desalination.

A miniature reciprocating expander is being developed as part of a larger program to develop a heat actuated heat pump for portable applications. By utilizing the higher energy density of liquid hydrocarbon fuels relative to batteries, a heat actuated heat pump would be able to provide cooling for much longer than motor driven units of equal weight. A prototype expander has been constructed and demonstrated to produce up to 22 W of shaft power at 2500 rpm using 60 psig, room temperature nitrogen as the input. Assuming adiabatic conditions, the expander appears to operate at up to 80% isentropic efficiency. However, when heat inflow to the expander is accounted for, the resulting polytropic efficiency is about 10% lower. In addition to experimental results, models of expander performance with different loss mechanisms are presented. These mechanisms include over- and under-expansion, in-cylinder heat transfer, clearance volume, friction, and valve pressure drop. / Graduation date: 2005

Miniature energy and chemical systems (MECS) are miniature thermal, fluid, and chemical devices in the mesoscale size range between a sugar cube and a human fist. MECS take advantage of improved rates of mass and heat transfer that have been observed at the microscale. There are many potential applications for MECS, including manportable cooling and decentralized chemical processing. However, this potential has not been realized due to limitations in microfabrication. MECS devices require: 1) the fabrication of complex geometries incorporating microscale features; and 2) the thermal, mechanical and chemical properties of engineering metals. This thesis centers on developing a process for producing high-aspect-ratio, MECS devices in stainless steel. In order to achieve this goal, laser ablation and diffusion bonding were employed in a metal microlamination (MML) process. The process involves stacking and bonding a series of laminates with low-aspect-ratio features to produce a composite device with high-aspect-ratio features (20:1). Laser ablation was used to form many laminates of 0.003" 302 stainless steel. These laminates were then joined via diffusion bonding. The process developed in this thesis is unique in that it: 1) permits the MECS designer greater freedom in specifying microchannel widths; and 2) has produced microscale features in excess of 20:1 aspect ratio. Microchannels and microfins in excess of 20:1 aspect ratio were fabricated in stainless steel using this method. Resultant microchannels were tested by flowing air through them at various flow rates and measuring the resulting pressure drop. Experimental results were compared with theoretical calculations and other technical literature. Findings suggest that the preliminary efforts to build a MECS device resulted in significant air blockage in the microchannel passageways. Sources of this blockage include bent fins, warpage and misalignment among others. Further process refinements are needed to prove the economic viability of this process. / Graduation date: 1998

Thesis (Ph.D.)--University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (February 28, 2007). Vita. Includes bibliographical references.

A robust understanding and planning of production enhancement and flow assurance is required as petroleum E&P activities are targeting deepwaters and long distances. Different flow assurance issues and their solutions are put together in this work. The use of multiphase pumps as a flow assurance solution is emphasized. Multiphase pumping aids flow assurance in different ways. However, the problem causing most concern is sand erosion. This work involved a detection-based sand monitoring method. Our objectives are to investigate the reliability of an acoustic sand detector and analyze the feasibility of gel injection as a method to mitigate sand erosion. Use of a sand detector coupled with twin-screw pumps is studied under varying flow conditions. The feasibility of gel injection to reduce slip and transport produced solids through twin-screw pump is investigated. A unique full-scale laboratory with multiphase pumps was utilized to carry out the experimental tests. The test results indicate that acoustic sand detection works in a narrow window around the calibration signature. An empirical correlation for predicting the twin-screw pump performance with viscous fluids was developed. It shows good agreement in the practical operational limits – 50% to 100% speed. The results indicate that viscous gel injection should be an effective erosion mitigation approach as it reduces slip, the principle cause of erosive wear. To correlate the performance of viscous fluid injection to hydroabrasive wear, further experimental investigation is needed.

An experimental and analytical study of a microchannel ammonia-water desorber was conducted in this study. The desorber consists of 5 passes of 16 tube rows each with 27, 1.575 mm outside diameter x 140 mm long tubes per row for a total of 2160 tubes. The desorber is an extremely compact 178 mm x 178 mm x 0.508 m tall component, and is capable of transferring the required heat load (~17.5 kW) for a representative residential heat pump system. Experimental results indicate that the heat duty ranged from 5.37 kW to 17.46 kW and the overall heat transfer coefficient ranges from 388 to 617 W/m2-K. The analytical model predicts temperature, concentration and mass flow rate profiles through the desorber, as well as the effective wetted area of the heat transfer surface. Heat and mass transfer correlations as well as locally measured variations in the heating fluid temperature are used to predict the effective wetted area. The average wetted area of the heat and mass exchanger ranged from 0.25 to 0.69 over the range of conditions tested in this study. Local mass transfer results indicate that water vapor is absorbed into the solution in the upper stages of the desorber leading to higher concentration ammonia vapor and therefore reducing the rectifier cooling capacity required. These experimentally validated results indicate that the microchannel geometry is well suited for use as a desorber. Previous experimental and analytical research has demonstrated the performance of this microchannel geometry as an absorber. Together, these studies show that this compact geometry is suitable for all components in an absorption heat pump, which would enable the increased use of absorption technology in the small capacity heat pump market.

A robust understanding and planning of production enhancement and flow assurance is required as petroleum E&P activities are targeting deepwaters and long distances. Different flow assurance issues and their solutions are put together in this work. The use of multiphase pumps as a flow assurance solution is emphasized. Multiphase pumping aids flow assurance in different ways. However, the problem causing most concern is sand erosion. This work involved a detection-based sand monitoring method. Our objectives are to investigate the reliability of an acoustic sand detector and analyze the feasibility of gel injection as a method to mitigate sand erosion. Use of a sand detector coupled with twin-screw pumps is studied under varying flow conditions. The feasibility of gel injection to reduce slip and transport produced solids through twin-screw pump is investigated. A unique full-scale laboratory with multiphase pumps was utilized to carry out the experimental tests. The test results indicate that acoustic sand detection works in a narrow window around the calibration signature. An empirical correlation for predicting the twin-screw pump performance with viscous fluids was developed. It shows good agreement in the practical operational limits – 50% to 100% speed. The results indicate that viscous gel injection should be an effective erosion mitigation approach as it reduces slip, the principle cause of erosive wear. To correlate the performance of viscous fluid injection to hydroabrasive wear, further experimental investigation is needed.

High efficiency air blowers to meet future portable aerosol sampling applications were designed, fabricated, and evaluated. A Centrifugal blower was designed to achieve a flow rate of 100 L/min (1.67 x 10^-3 m^3/s) and a pressure rise of WC " 4 (1000 PA). Commercial computational fluid dynamics (CFD) software, FLUENT 6.1.22, was used extensively throughout the entire design cycle. The machine, Reynolds number (Re) , was around 10^5 suggesting a turbulent flow field. Renormalization Group (RNG) κ−ε turbulent model was used for FLUENT simulations. An existing design was scaled down to meet the design needs. Characteristic curves showing static pressure rise as a function of flow rate through the impeller were generated using FLUENT and these were validated through experiments. Experimentally measured efficiency (ηEXP) for the base-design was around 10%. This was attributed to the low efficiency of the D.C. motor used. CFD simulations, using the κ−ε turbulent model and standard wall function approach, over-predicted the pressure rise values and the percentage error was large. Enhanced wall function under-predicted the pressure rise but gave better agreement (less than 6% error) with experimental results. CFD predicted a blower scaled 70% in planar direction (XZ) and 28% in axial direction (Y) and running at 19200 rpm (70xz_28y@19.2k) as the most appropriate choice. The pressure rise is 1021 Pa at the design flow rate of 100 L/min. FLUENT predicts an efficiency value based on static head (ηFLU) as 53.3%. Efficiency value based on measured static pressure rise value and the electrical energy input to the motor (ηEXP) is 27.4%. This is almost a 2X improvement over the value that one gets with the hand held vacuum system blower.

Thesis (Ph.D)--Mechanical Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Garimella, Srinivas; Committee Member: Allen, Mark; Committee Member: Fuller, Tom; Committee Member: Jeter, Sheldon; Committee Member: Wepfer, William. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis (Ph. D. (Plant Production))--University of Pretoria, 2001. / Adobe Acrobat Reader needed to open files.