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Articles 1 - 7 of 7

Full-Text Articles in Mechanical Engineering

Optimization Of Titanium Liquid/Gas Diffusion Layers In Proton Exchange Membrane Electrolyzer Cells, Stuart Mccoy Steen Dec 2015

Optimization Of Titanium Liquid/Gas Diffusion Layers In Proton Exchange Membrane Electrolyzer Cells, Stuart Mccoy Steen

Masters Theses

Polymer electrolyte membrane electrolyzer cells (PEMECs), which are reverse PEM fuel cells (PEMFCs), are effective energy storage medium by producing hydrogen/oxygen from water using electricity from renewable energy sources. This is due in part because of its efficiency, high energy density, compact design, and large capacity. In a PEMEC, a liquid/gas diffusion layer (LGDL) is located between the catalyst layer and the current distributing flow field. The LGDL is expected to transport electrons, heat, and reactants/products to and from the catalyst layer with minimum voltage, current, thermal, interfacial, and fluidic losses. Carbon materials (carbon paper or carbon ...


Impurity Effects In All-Vanadium Redox Flow Batteries, Andrew William Burch Dec 2015

Impurity Effects In All-Vanadium Redox Flow Batteries, Andrew William Burch

Masters Theses

In this dissertation, the effects of VOSO4 [vanadyl sulfate] source and impurities on the beginning-of-life (BOL) performance of an all-vanadium redox flow battery (VRFB) are explored. Battery performance was monitored at 50% state of charge (SOC) using electrolyte with VOSO4 purities of 99%, 99.9% and 99.99% by weight. At cell potentials of 1.23V, the least pure solution yielded the lowest current density of 280 mA/cm2 [square centimeter] and the most pure solution yielded the highest, 560 mA/cm2. The voltage efficiencies and charge-discharge capacities were shown to follow the same trends. Scanning ...


Modeling And Validation Of Heat Transfer Present In A Solar Thermal Collector, Eric Ezekiel Stannard Dec 2013

Modeling And Validation Of Heat Transfer Present In A Solar Thermal Collector, Eric Ezekiel Stannard

Masters Theses

A solar absorber panel for a solar water heating system located at the College of Architecture’s New Norris House in Norris, TN was modeled and validated against field data in this work. The purpose of this modeling was to create the foundations of a tool that can be used in collector design and building energy simulations. This tool would take into account the radiometric properties of the collector materials, which are essential for an accurate model. Solar water heaters convert the shortwave energy of the Sun into usable heat for residential and industrial applications and have the potential to ...


Water Transport In Polymer Electrolyte Fuel Cells: An Exploration Of Net Water Drag In Real Time, Susan Katherine Reid May 2013

Water Transport In Polymer Electrolyte Fuel Cells: An Exploration Of Net Water Drag In Real Time, Susan Katherine Reid

Masters Theses

Polymer electrolyte fuel cells (PEFCs) are a promising alternative energy source. One challenge preventing widespread use of this technology is water management. A balance must be reached between providing sufficient water for membrane ionic conductivity while maintaining low enough water content to mitigate the reduction of available reaction sites in the cathode catalyst layer due to liquid water build up. Much exploration of this area of fuel cell research has been conducted, but the details of water transport in an operating fuel cell are not yet fully understood. The motivation of this work was to elucidate mass transport phenomena occurring ...


Droplet Characterization In The Wake Of Steam Turbine Cascades, Adam Charles Plondke May 2012

Droplet Characterization In The Wake Of Steam Turbine Cascades, Adam Charles Plondke

Masters Theses

In low-pressure steam turbines, water droplet formation on the surfaces of stationary stator blades can lead to erosion on downstream turbine blades and other equipment. One property that affects the size of the droplets that are formed is the adhesive forces between the water and the surface of the stator blade. The adhesive forces hold the droplets to the surface where they may combine, forming increasingly larger droplets. Eventually, the aerodynamic forces will tear the droplets off the surface, carrying them downstream.

To study the effect of stator surface properties on the droplet size distribution, four cascades of stator blades ...


Cross-Flow, Staggered-Tube Heat Exchanger Analysis For High Enthalpy Flows, Gary L. Hammock May 2011

Cross-Flow, Staggered-Tube Heat Exchanger Analysis For High Enthalpy Flows, Gary L. Hammock

Masters Theses

Cross flow heat exchangers are a fairly common apparatus employed throughout many industrial processes. For these types of systems, correlations have been extensively developed. However, there have been no correlations done for very high enthalpy flows as produced by Arnold Engineering Development Center’s (AEDC) H2 facility. The H2 facility uses a direct current electric arc to heat air which is then expanded through a converging-diverging nozzle to impart a supersonic velocity to the air. This high enthalpy, high temperature air must be cooled downstream by the use of a cross flow heat exchanger.

It is of interest to evaluate ...


Thermal Feasibility And Performance Characteristics Of An Air-Cooled Axial Flow Cylindrical Power Inverter By Finite Element Analysis, Jonathan Atef Tawfik May 2011

Thermal Feasibility And Performance Characteristics Of An Air-Cooled Axial Flow Cylindrical Power Inverter By Finite Element Analysis, Jonathan Atef Tawfik

Masters Theses

The purpose of the present study is to determine the thermal feasibility of an air-cooled power inverter. The inverter circuitry layout is designed in tandem with the thermal management of the devices. The cylindrical configuration of the air-cooled inverter concept accommodates a collinear axial air blower and a cylindrical capacitor with inverter cards oriented radially between them. Cooling air flows from the axial fan around the inverter cards and through the center hole of the cylindrical capacitor. The present study is a continuation of the thermal feasibility study conducted in fiscal year 2009 for the Oak Ridge National Laboratory to ...