Multiple oscillating heat spreaders (OHS) were fabricated for the purpose of effectively transporting heat fluxes from vehicular electronics. The OHSs possessed modified evaporators for enhanced thermal spreading capabilities; one OHS was designed for pressure shorting, i.e. the ‘Slots OHS’, and the other for thermal shorting, i.e. the ‘Perforated Evaporator OHS’. These OHSs were tested in the axial heating configuration with the evaporator length-wise opposite the condenser, as well as in a centralized heating configuration implemented with the condenser thick-wise opposite the heat source to characterize thermal spreading effectiveness. The condensing location and heat input were varied in the central heating and axial configuration to determine thermal spreading effectiveness dependency to condenser location, heat removal, and heat input. Both OHSs were experimentally compared to an OHS of similar dimensions with no modified evaporator, and the results indicate the modified evaporators improve OHS thermal spreading ability for high heat flux thermal management.

Oscillating heat pipes (OHPs) have been actively investigated since their inception due to their ability to manage high heat/heat fluxes. The OHP is a passive, wickless, two-phase heat transfer device that relies on pressure driven fluid oscillations within a hermetically-sealed serpentine channel structure. The cyclic phase-change heat transfer drives additional sensible heat transfer, and this combination causes OHPs to have high effective thermal conductivities. Many strides have been made, through both experimentation and modeling, to refine the design and implementation of OHPs. However, the main objective in OHP research has been to better understand the thermodynamic and fluid mechanic phenomena so as to enhance OHPs' thermal performance. The current work presents methods for using OHP in thermal-to-electric energy harvesting, which would allow for ‘dual-purpose’ OHP applications in which thermal management can be combined with work output. Energy harvesting occurred when a portion of the thermally-driven fluidic motion was used to generate a voltage either by electromagnetic induction or by a piezoelectric transducer imbedded in an OHP tube. For the induction approach, two methods were used to create the time-varying magnetic field required for induction. In the first, a ferrofluid was used as the OHP working fluid. Because the magnetic dipoles of the nanoparticles are randomly aligned naturally, two static, external ‘bias’ magnets were required to create a uniform magnetic field to align the particle dipoles for a non-zero magnetic flux change through a coaxial solenoid. The second method used a small rare-earth magnet confined inside a set length of an OHP channel that had a coaxial solenoid. As the OHP working fluid moved inside the harvesting channel, a portion of the fluid's momentum was transferred to the magnet, causing it to oscillate. For the piezoelectric approach, a narrow piezoelectric transducer was placed in a bow-shaped configuration along the inside of an OHP channel. Passing fluid would deflect the piezo creating a potential difference across its leads, which protruded out of the channel walls. All three of these methods successfully produced a voltage while retaining the excellent thermal performance synonymous with OHPs.

An experimental study of turbulent air flow in a pipe is reported in this paper. A determination was made of the mean velocity distribution and longitudinal mean turbulent velocity distribution, both in the turbulent core and boundary layer for four different Reynolds numbers from 7300 to 58300. A traversing mechanism was designed in order to measure the turbulence correlations between two points. The variation of the macro scale length, one of the fundamental quantities in recent statistical turbulence theory across the pipe diameter was calculated for Reynolds number equal to 58300, by integrating the correlation curves. The turbulent momentum diffusivity at the center of a pipe was calculated from the correlation study and the dimension less value was found to be 0.111. Ethylene gas was injected into the center of the pipe, and in order to investigate the turbulent mass diffusivity, the concentration distribution curves of ethylene were measured at different test positions downstream from the injection point, for the same series of Reynolds numbers used in the turbulence measurement. A numerical method for calculating the diffusivity was developed. The values of diffusivity obtained. in these experiments show that the assumptions which were used by most of the authors, that of (turbulent mass diffusivity/turbulent momentum diffusivity) has a value between 1.0 to 1.6 is correct. / Thesis / Master of Engineering (ME)

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An examination of various methods for mass flow rate measurements was undertaken to evaluate their applicability for measuring refrigerant R-134a two-phase mass flow in refrigeration and air-conditioning equipment. An experimental apparatus was constructed to generate the required two-phase flow conditions. A turbine and a venturi flowmeter were used together with either a capacitance transducer or a gamma densitometer to determine the two-phase mass flow rate. The time-averaged void fraction was measured using a capacitance transducer and a gamma densitometer. Their measurements were in good agreement. Hence, for mass flow rate measurements, the capacitance transducer was used as the void fraction meter because of its ease of operation. A number of models were used to combine the output of either the turbine flowmeter or the venturi flowmeter, with the void fraction measurement to estimate the mass flow rate. It was found that, within the range of experimental data tested in the present work, the venturi flowmeter, in conjunction with Chisholm's model, provided the best agreement with the experimental results. / Thesis / Master of Engineering (MEngr)

While more than 100 years of research has focused on removing acute and chronic health threats from water, substantially less study has focused on potable water infrastructure and water quality deterioration, monitoring technologies, and relationships between water taste and consumer health. These knowledge–gaps have left infrastructure users, owners, regulators, and public health professionals largely unaware of how premise and buried polymer water pipes deteriorate and sorb/ desorb organic contaminants during normal operations and following water contamination events. These knowledge–gaps also prevent infrastructure managers from producing drinking water that optimizes mineral content for both water taste and health benefits, and employing a monitoring tool capable of immediately detecting water contamination or equipment failures. Research was conducted to address these challenges using analytical chemistry, environmental engineering, food science, polymer chemistry, public health, and material science principles. This work was enhanced by collaborations with sixteen American water utilities and the National Institute for Standards and Technology. These efforts were funded by the National Science Foundation, American Water Works Association, and the Water Research Foundation. Research results are unique and provide important scientific contributions to the public health, potable water, and material science industries. Particular achievements include the: (1) Evaluation of linkages between minerals, water palatability, and health useful for water production and public health decisions; (2) Creation of a novel infrastructure and water quality surveillance tool that has begun water utility implementation in the USA; (3) Development of an accelerated chlorinated water aging method with stable water pH, free chlorine, and alkalinity concentration that enables interpretation of polymer pipe surface and bulk characteristic changes; (4) Discovery that polar compounds are 2–193% more soluble in PEX than HDPE water pipes; (5) Finding that several polymer and contaminant properties can be used to predict contaminant diffusivity and solubility during sorption and desorption in new, lab aged, and water utility PE pipes; and the (6) Discovery that chlorinated water exposure of HDPE and PEX pipes increases polar contaminant diffusivity during sorption by 50–162% and decreases diffusivity during desorption as much as 211%. Outcomes of this work have domestic and global significance, and if engaged, can greatly improve public health protection, potable water infrastructure operations, water quality, sustainability, and regulation. / Ph. D.