Mechanical Engineering Commons^™

Understanding Thermal Comfort Impact And Air Movement Around Open Stairs Through The Use Of Cfd Modeling, Ethan Davidson

Graduate Theses and Dissertations

The air exchange between two floors of a building has an impact on thermal comfort. The present research attempts to quantify this impact and identify the contributing factors disrupting the thermal comfort on and around stairs. Various heating and cooling scenarios were analyzed, using CFD modeling, in a simple two-story building separated by a single staircase. The research examines a single building layout with a fixed inlet and outlet configuration. In addition, the study investigated the short-term impact on thermal comfort. As a result, the duration of the simulations varies from two and half minutes to ten minutes, consistent with …

Enhancing Stability Of High-Nickel Cathodes For Lithium-Ion Batteries Through Additive Manufacturing Of Cathode Structure, Matthew Sullivan

Mechanical Engineering Undergraduate Honors Theses

Lithium-ion batteries (LIBs) are currently the best method to store electrical energy for use in portable electronics and electronic vehicles. New cathode materials for LIBs are consistently studied and researched, but few are as promising and attainable as nickel-rich transition metal oxides such as LiNi1-x-yMnxCoyO2 (NMC). NMC materials exist with many different mass ratios, but higher nickel content materials provide higher energy density. With this increase in capacity comes a sacrifice with cyclability, as high-nickel NMC variants are prone to structure collapse, transition metal dissolution, and cracks due to volume change. In this report, mechanical modification of the electrode by …

Hobby Grade Lithium-Ion Batteries For Spacecraft Applications: Establishing An Automated Electrical Characteristics Testing Procedure For Flight Acceptance Of Non-Space-Grade Small Secondary Batteries, Braidon Hughes

Graduate Theses and Dissertations

Li-ion batteries are widely used due to the large amount of rechargeable energy they pack into a small, light package. This higher energy density makes Li-ion batteries ideal for small satellite applications, specifically CubeSats. CubeSats have grown in popularity in higher level education due to the National Aeronautics and Space Administration’s implementation of the Cube Satellite Launch Initiative, making it easier and cheaper to conduct small, low orbit missions. Because these CubeSats are occupying the same space as a crewed spacecraft, it is imperative that they are safe. There are numerous reports of Li-ion batteries creating fires that result in …

Nonmetallic Jet Impingement Thermal Management For Power Electronics Via Additive Manufacturing, Reece Whitt

Graduate Theses and Dissertations

The increase in energy demanded by transportation and energy sectors has necessitated highly efficient thermal management for reliable power electronics operations. Conventional cooling techniques are limited by their inability to target switching location hot spot temperatures, leading to non-uniform thermal gradients. These devices, such as cold plates and heat sinks, also utilize heavy metallic structures that can accentuate electromagnetic interferences generated by high voltage switching processes. This work proposes a non-metallic jet impingement cooler for more customized thermal management, while simultaneously reducing the harmful effects of electromagnetic interferences. Additive manufacturing is utilized to enable jet impingement zones to target individual …

Tribological Studies Of Thick Polytetrafluoroethylene Coatings Enhanced By Polydopamine And Nanoparticles, Sujan Kumar Ghosh

Graduate Theses and Dissertations

Polytetrafluoroethylene (PTFE) is a popular low friction solid lubricant with high chemical and thermal stability. Thick PTFE coatings have the potential for many tribological applications, such as replacing Tin-based Babbitt materials in journal bearings. However, the weak bonding strength to the substrate and the high wear rate of PTFE coatings are current limiting factors. The lack of understanding of their tribological properties and wear mechanisms in oil-lubricated conditions and how coating thickness affects the tribological performance further hindered the use of PTFE coatings. In this dissertation, polydopamine (PDA), a bio-inspired adhesive, is used as an underlayer for or as a …

Development Of Novel Battery Materials For Lithium-Ion Batteries And Beyond, Jiyu Cai

Graduate Theses and Dissertations

As fossil fuels are depleting and causing environmental issues, it becomes imperative to widely implement renewable energies (e.g., solar and wind power). In this context, electrical energy storage (EES) systems are essential to accommodate the intermittent supply and uneven distribution of renewable energies. To this end, high-energy-density EES devices are highly demanded, such as rechargeable batteries. This dissertation presents my efforts in developing novel battery materials for lithium-ion batteries (LIBs), sodium-ion batteries (SIBs), and solidstate lithium batteries (SSLBs). These efforts include electrochemical evaluations of battery materials, surface modifications of electrodes via atomic layer deposition (ALD), and advanced characterizations of batteries …

High Temperature Degradation In Gan-Based Hall Effect Sensors, Alexis Anne Krone

Graduate Theses and Dissertations

This research focuses on understanding the effects of accelerated aging through temperature and environment on novel gallium nitride-based Hall effect magnetic field sensors and determining device reliability under electric vehicle operating conditions. The device reliability was modeled using accelerated aging for the temperatures of 200 °C, 350 °C, 450 °C, and 600 °C under various time steps unique to each temperature and either air, which is identical to operating circumstances, or argon, which would model the hermetic packaging environment. Using a high temperature furnace and oven, devices underwent high temperature storage tests at a chosen temperature and time step. Afterwards, …

Performance And Economics Of Solar Inverters And Module Level Power Electronics In A 1 Mw Photovoltaic System, Maxwell Criswell

Biological and Agricultural Engineering Undergraduate Honors Theses

Photovoltaic solar panels convert sunlight to electricity in the form of direct current; therefore, a necessary component of every photovoltaic system is an inverter to convert the electricity to usable alternating current. There are various commercially available inverter technologies manufactured today such as microinverters, string inverters, and central inverters, as well as module level power electronic devices such as DC optimizers that are capable of improving system performance in string and central inverter systems. This thesis compares the performance and economics of five different inverter and module level power electronic systems through model simulation using Helioscope software. The five alternatives …

Nanoscratch Study Of Diamond-Like Carbon Coatings With A Polydopamine + Sio2 Adhesive Underlayer, Anna Fisher

Mechanical Engineering Undergraduate Honors Theses

Diamond-like carbon (DLC) coatings have a wide array of desirable characteristics such as low friction, high hardness, and scratch resistance. Due to high residual stress and thermal mismatch, DLC films experience adhesion difficulties when bonded with metallic substrates, leading to cracking and delamination. In this study, the properties of a new coating with a polydopamine underlayer and silica nanoparticles bonded to a stainless-steel substrate (PDA+SiO2/DLC) were studied alongside three other samples, one with a polydopamine underlayer (PDA/DLC), one with a trimethylsilane (TMS) underlayer (TMS/DLC), and one with no underlayer (DLC only). Nanoscratch tests were performed with a 1 μm spheroconical …

Economic Feasibility Of Mixed Plastic Waste Pyrolysis Using Twin Reactor System In Northwest Arkansas, Carol Rogers, Patricia Means, Renato Gonzalez, Kaida Sheets, Hayden Townsend

Chemical Engineering Undergraduate Honors Theses

Plastic waste generation is increasing at an unsustainable rate while recycling solutions remain stagnant. As a chemical means of recycling, mixed plastic waste pyrolysis can generate synthetic oil appropriate for use as fuel in power generation from plastic waste that otherwise accumulates in landfills. With the scaling of a commercial plastic pyrolysis process in Northwest Arkansas (NWA) modeled after an operational sawdust pyrolysis unit in Huntsville, Arkansas, economic analysis resulted in 26.3% internal rate of return. Therefore, construction of a commercial mixed plastic-to-fuel pyrolysis plant is economically justified and should be pursued. To effectively implement the proposed design, NWA must …

A History And Status Of Wind Energy Potential In Arkansas, Pre And Post Covid-19, Will Blasingame

Mechanical Engineering Undergraduate Honors Theses

Historically, wind-generated electricity has been the largest renewable energy sources in the United States. Wind-rich regions like Oklahoma and Texas have fueled growth and sold that electricity to electric utilities located in wind-poor states like Arkansas in the form of Power Purchase Agreements. Future technologies such as Vertical Axis Wind Turbines, small wind turbines, and Tesla turbines designed to generate electricity from wind show promise in unlocking more expensive wind resources in regions like Northwest Arkansas by mitigating concerns about low wind speeds and noise. However, more factors than just feasibility influence the growth of wind power. Governmental policies such …

Hvac System Energy Audit For Leverett Elementary School, Connor Smalling

Biological and Agricultural Engineering Undergraduate Honors Theses

Leverett Elementary School is located in Fayetteville, AR. The school needs significant upgrades to its infrastructure. The Fayetteville Public School District has voted to pursue an Energy Services Performance Contract (ESPC) in order to finance the desired upgrades to Leverett Elementary, among other schools in the district.

The scope of this thesis was to perform an energy audit on the existing heating, ventilation, and air conditioning (HVAC) system. By using an energy modeling software, eQuest, the building and the existing base system were modeled to determine utility consumption. Three different HVAC system alternatives were analyzed against the base system by …

Challenges And Opportunities Of Layered Cathodes Of Linixmnyco(1-X-Y)O2 For High-Performance Lithium-Ion Batteries, Jason Frank

Mechanical Engineering Undergraduate Honors Theses

High energy density lithium-ion batteries (LIBs) are widely demanded for portable electronic devices and electrical vehicles. Layered-structure LiCoO₂ oxide (LCO) has been the most commonly used cathode material in commercial LIBs. Compared to LCO, LiNi_1-x-yMn_xCo_yO₂ (NMC) cathodes are particularly attractive due to their reduced cost and higher capacity. Among the NMC cathodes, nickel-containing LiNi_0.5Co_0.3Mn_0.2O₂ (NMC532) is one of the most promising cathode materials undergoing intensive investigation, but suffers from a series of technical issues, such as structural instability, performance fading, and safety issues. In this …

Bgaas Alloy Semiconductors For Lasers On Silicon, Joshua Mcarthur

Mechanical Engineering Undergraduate Honors Theses

In the world of semiconductors today, there is a large dissonance between optical devices and electrical application. Due to the limitations of electron transport, photonic integrated circuits are soon-to-be vital in fields like telecommunications and sensing. Right now, these PIC’s are mostly made from indium phosphide. Due to its ubiquitous nature, however, there is a huge push to integrate efficient optics with silicon. It’s cheap, abundant, dope-able, and our electronic infrastructure is based on it. The reason why silicon photonics aren’t already commercialized is because of silicon’s indirect bandgap—it is inefficient with optical applications. The problem with combining direct gap …

Towards Environmentally Sustainable And Cost-Effective Food Distribution In The U.S., Jasmina Burek

Graduate Theses and Dissertations

Distribution centers (DCs) and supermarkets have an important role in food sustainability, but no previous research has accounted for their environmental impact. The purpose of this research was to assess environmental sustainability of grocery, perishables, and general merchandise DCs; to estimate food storing and retailing impact; and to provide cost-effective strategies to reduce DCs’ environmental impacts. The importance and relevance of the research is threefold: improving sustainability of DCs, food storing, and food retailing. The main method used in this research was the life cycle assessment (LCA) method. An initial study calculated environmental impacts of the Wal-Mart Stores, Inc. DCs, …

Interfacial Tailoring Of Lithium-Ion Batteries By Atomic/Molecular Layer Deposition, Qian Sun

Graduate Theses and Dissertations

Lithium-ion batteries (LIBs) are promising energy storage devices, which play significant roles in addressing problems related to fossil fuels depletion and environmental pollution. Since the 1990s, LIBs have attracted great attention for many applications. Nowadays, LIBs are dominating portable electronics, having several advantages over their forerunners, such as high voltage (3.3~4.2 V) [1,2], low self-discharge (< 5~10 %/month) [3,4], wide operation temperature (-20~60 °C) [5,6], and fast charge/discharge rate [7,8]. However, LIBs deliver an energy density of 100-220 Wh/kg in practice to date, which is far from their theoretical ones, thus hindering their further applications in electric vehicles. Additionally, LIBs have been plagued by other problems, such as intolerance to overcharge/overdischarge, low heat resistance, lithium dendrites growth, large volume change of the silicon anode, large polarization and even safety problems.

Atomic layer deposition (ALD) and molecular layer deposition (MLD) are two important techniques, both proceeding in self-limiting gas-solid reactions and exhibiting excellent capabilities for ultra-thin films, conformal coatings, and controllable growth. They can be employed to address the problems of LIBs mentioned above by …

Intelligent Application Of Flexible Ac Transmission System Components In An Evolving Power Grid, Robert Wall

Graduate Theses and Dissertations

The world revolves around energy and the energy sector is continually transforming and evolving. The status quo has been set by governing agencies in the United States for completely reliable power. The demand for energy efficiency continually rises for multiple reasons. Technology has improved for all sectors of the power grid, including renewable energy sources, fault protection, and SMART grid technology. The addition of new energy sources has led to the decommissioning of inefficient energy sources. The implementation of new technologies and power load on a large scale, coupled with the removal of grid stabilizers has posed different challenges that …

Design Of Wind Turbine Tower Height And Blade Length: An Optimization Approach, Ryan Wass

Mechanical Engineering Undergraduate Honors Theses

The wind industry is a fast growing market and is quickly becoming competitive with traditional non-renewable energy resources. As with any developing industry, research must continually be redefined as more complex understandings of design variables are learned. Optimization studies are common ways to quickly refine design variable selections. Historical wind turbine data shows that the tower hub height to rotor diameter ratio scales almost linearly. However there is no specific rule that dictates the optimum hub height for a given diameter. This study addresses this question by using an Excel based optimization program to determine the height to diameter ratio …

Fluid Phase Separation Via Nanochannel Array, John Lee

Graduate Theses and Dissertations

Microelectromechanical systems (MEMS) and nanoelectromechanical systems (NEMS) generate ideas and techniques for creating new devices at the micro/nano scale. This dissertation study designed a gas generator system utilizing nanochannels for phase separation that is useful for micro-pneumatic actuators, micro-valves, and micro-pumps. The new gas generator has the potential to be an integral part of a propulsion system for small-scale satellites. Nano/picosatellites have limited orientation capability partly due to the current limitations of microthruster devices. Development of a self-contained micro propulsion system enables dynamic orbital maneuvering of pico- and nano-class satellites.

Additionally, the new gas generator utilizes a high efficiency, green …

Non-Covalent Functionalization Of Graphene Films For Uniform Nanoparticle Deposition Via Atoic Layer Deposition, Ty Seiwert

Mechanical Engineering Undergraduate Honors Theses

Graphene functionalized with platinum (Pt) and palladium (Pd) has proven to be highly effective as a hydrogen sensor. Deposition methods such as Atomic layer deposition (ALD) can be further enhanced by pretreating the graphene with a non-covalent surfactant prior to nanoparticle deposition. In this study, graphene-based sensing devices will be fabricated by ALD deposition. The graphene will be non-covalently functionalized using sodium dodecyl sulfate (SDS) anionic surfactant prior to ALD deposition. The aim of this study is to test the deposition pattern achieved by varying the amount of time that graphene is treated with the SDS surfactant. Initially, ALD deposition …

Exploring Energy, Comfort, And Building Health Impacts Of Deep Setback And Normal Occupancy Smart Thermostat Implementation, Zachary Ethan Alderman

Graduate Theses and Dissertations

As smart thermostat adoption rates continue to increase, it becomes worthwhile to explore what unanticipated outcomes may result in their use. Specific attention was paid to smart thermostat impacts to deep setback and normal occupancy states in a variety of conditions while complying with the ventilation and temperature requirements of ASHRAE 90.2-2013. Custom weather models and occupancy schedules were generated to efficiently explore a combination of weather conditions, building constructions, and occupancy states. The custom modeling approach was combined with previous experimental data within the Openstudio graphics interface to the EnergyPlus building modeling engine. Results indicate smart thermostats add the …

A Spreadsheet Algorithm For Determining The Economic Feasibility Of Micro-Chp Systems In The Arkansas Manufacturing Sector, Ford R. Lewallen

Graduate Theses and Dissertations

Combined heat and power (CHP) systems are not new to the market. However, advances in technology, specifically MicroTurbines, have presented new opportunities for installations of micro-CHP units - defined as 50 kWe to 300 kWe, specifically at small- to medium-sized industrial facilities. One pressing concern is whether or not an industrial plant has a high enough process thermal load requirement to fully utilize the energy output.

This thesis will discuss simulations that were run on several actual electric and thermal load combinations, which correspond to types of manufacturing facilities commonly found in Arkansas. Analysis of the plant usage profiles will …

An Economic Analysis Of Residential Photovoltaic Systems With And Without Energy Storage, Rodney Moses Kizito

Graduate Theses and Dissertations

Residential photovoltaic (PV) systems serve as a source of electricity generation that is separate from the traditional utilities. Investor investment into residential PV systems provides several financial benefits such as federal tax credit incentives for installation, net metering credit from excess generated electricity added back to the grid, and savings in price per kilowatt-hour (kWh) from the PV system generation versus the increasing conventional utility price per kWh. As much benefit as stand-alone PV systems present, the incorporation of energy storage yields even greater benefits. Energy storage (ES) is capable of storing unused PV provided energy from daytime periods of …

System-Layout-Dependent Thermally Induced Solder Stress & Reliability Implications, Ange C. Iradukunda

Mechanical Engineering Undergraduate Honors Theses

Electronic flip chip assemblies consist of dissimilar component materials, which exhibit different CTE. Under thermal cyclic operating conditions, this CTE mismatch produces interfacial and interconnect stresses, which are highly dependent on system layout. In this paper, sensitivity analyses are performed using ANSYS FEA to establish how the proximity and arrangement of neighboring devices affect interconnect stress. Flip chip alignment modes ranging from edge-to-edge to corner-to-corner are studied. Results of these FEA studies, demonstrated that closely packing devices together has the effect of making them act as one. This results in a significant increase in the thermomechanical stresses induced on peripheral …

Industrial Energy Consumption, Benchmarking, And Analysis In The United States, Daniel Maldonado

Mechanical Engineering Undergraduate Honors Theses

The purpose of this paper is to analyze the energy consumption of the industrial sector in the United States, and to identify the tools that can be used to minimize the consumption and improve the energy efficiency of all facilities in the country. The first part of the paper is a historical analysis of the industrial sector energy consumption, where the different energy sources are identified. The second part details different electronic tools that will provide facilities the ability of performing benchmarking, in order to understand their energy performance. Finally, the third part of this paper provides information about the …

A Look At Commercial Building Energy Use And Energy Efficiency Technologies From 1980 To Present, Marvin M. Arroyo

Mechanical Engineering Undergraduate Honors Theses

Energy consumption has increased considerably in the last fifty years as population rises. At the same time, design and efficiency of all equipment used in commercial buildings have changed as well. The purpose of this thesis is to explain how HVAC systems have changed and how they have affected energy consumption. Entities like the US Department of Energy (DOE) and the US Energy Information Administration (EIA) facilitate the data-gathering process by offering databases of energy information from actual monthly energy bills to promote public understanding of energy and its interaction with the economy and the environment. Moreover, in order to …

Improved Methods For Identifying, Applying, And Verifying Industrial Energy Efficiency Measures, Andrew Chase Harding

Graduate Theses and Dissertations

Energy efficiency is the least expensive source of additional energy capacity for today's global energy expansion. Energy efficiency offers additional benefits of cost savings for consumers, reduced environmental impacts, and enhanced energy security. The challenges of energy efficiency include identifying potential efficiency measures, quantifying savings, determining cost effectiveness, and verifying savings of installed measures. This thesis presents three separate chapters which address these challenges. The first is a paper presented at the 2014 industrial energy technology conference (IETC) that details a compressed air system project using the systems approach to identify cost effective measures, energy intensity to project savings, and …

Maximum Power Point Tracking And Solar Power For Developing Countries Around The World, Christopher M. Plate

Electrical Engineering Undergraduate Honors Theses

Renewable energy is becoming increasingly important as more and more countries become industrialized. Using solar power as opposed to fossil fuels and coal is becoming cheaper and easier to access throughout the world, yet there are still efficiency hurdles to be overcome. Designing a cheap, easily modifiable and reparable Maximum Power Point Tracker would be a stepping stone to bringing solar power to remote parts of the globe. Once designed and made portable, these devices could be distributed throughout developing countries to enhance renewable energy output. An Arduino-based tracker was chosen for ease of use and access. This base also …

Experimental Verification And Integration Of A Next Generation Smart Power Management System, Tavis Clemmer

Graduate Theses and Dissertations

With the increase in energy demand by the residential community in this country and the diminishing fossil fuel resources being used for electric energy production there is a need for a system to efficiently manage power within a residence. The Smart Green Power Node (SGPN) is a next generation energy management system that automates on-site energy production, storage, consumption, and grid usage to yield the most savings for both the utility and the consumer. Such a system automatically manages on-site distributed generation sources such as a PhotoVoltaic (PV) input and battery storage to curtail grid energy usage when the price …

Energy Consumption And Greenhouse Gas Emissions From Commercial And Manufacturing Sectors Specific Studies On Hvac Equipment And Dairy Processing, Aik Jong Tan

Graduate Theses and Dissertations

Commercial and manufacturing sectors in United States consumed approximately 50% of the total End use energy in 2010. In 2009, 81.5% of the greenhouse gas (GHG) emitted in the United States was energy related. From the broad aspects of commercial and manufacturing sectors; two relatively narrow and specific topics, commercial building's HVAC equipment and dairy processing were chosen to increase the understanding of the energy use and GHG emission in these two sectors. Few published studies related to these two specific areas are available. The first study in this thesis discussed the energy use and GHG emissions by HVAC equipment …