Mechanical Engineering Commons^™

Thermal Resistance Characterization Of High-Voltage Sic Power Module, Landon Lemmons

Mechanical Engineering Undergraduate Honors Theses

Researchers within the University of Arkansas Electrical Engineering Research Department have embarked on a project aimed at enhancing the thermal performance of high-voltage power modules. To aid in the progress of this project, the design, and development of a thermal tester device are needed. The primary objective of this device is to determine the various thermal properties of high-voltage power modules that the electrical engineering department has developed. Additionally, the project aims to facilitate electrical loading tests on power modules and provide researchers with the means to calibrate the power module in terms of thermal load. This project also possesses …

Design And Characterization Of A High Pressure Flow Loop For Heat Transfer Experiments Of Supercritical Carbon Dioxide, Joseph Sauerbrun

Doctoral Dissertations and Master's Theses

Supercritical carbon dioxide (sCO2) sees heightened heat transfer characteristics near its critical point due to its drastically changing thermophysical properties. Conventional single phase heat transfer theory was not developed to capture this nonlinear variation in properties and cannot predict the heat transfer characteristics of sCO2 to a practical level useful for design. To delve deeper into the behavior near the critical point and shed light on this crucial phenomenon, a state-of-the-art closed flow loop was developed. This setup enabled convective heat transfer experiments of sCO2 under diverse boundary conditions and test section geometries. Key components of the loop include the …

A Systematic Study Into The Design And Utilization Of Burn Wire As A Means Of Tensioning And Releasing Spacecraft Mechanisms Through Applied Joule Heating, Chandler Dye

Mechanical Engineering Undergraduate Honors Theses

The joule heating characteristics of Nichrome burn wires, often used as a thermal cutting device in mechanisms designed to fasten and release CubeSat deployables, are examined in the following thesis. Wires ranging from 0.125 inches to 2 inches long, and diameters of 30 Ga and 40 Ga, are investigated through analytical calculations and thermal simulations based on heat transfer due to joule heating, and through physical circuitry-based experiments. The temperature data is used to generate heating curves to predict the time it takes for Nichrome wires to fail under varying testing parameters. This research aims to catalog a series of …

Numerical Investigation Of Flow And Thermal Behavior In Channels With Pcm-Filled Thermal Energy Storage Columns For Potential Application In Photobioreactors, Sameed Akber

Electronic Thesis and Dissertation Repository

Microalgae has been identified as a potential source in the production of biofuel. Photobioreactors, which are used for microalgae production, normally experience temperature variations over the diurnal cycle due to changes in ambient conditions. The thermal regulation of photobioreactors to minimize temperature variations will result in a higher yield of microalgae, which are sensitive to such variations. The present research is aimed to investigate a novel approach to thermally regulate photobioreactors using phase change materials (PCM) where the latent heat of the material is exploited as the energy storage. The present research uses a numerical approach to study the flow …

Heat Pipes With Arbitrary Boundary Conditions, Katrina Sweetland

Doctoral Dissertations

Heat pipes passively transfer heat in numerous applications. Traditionally one side of the heat pipe is coupled to a heat source (evaporator) while the opposite side is coupled to a heat sink (condenser). This configuration has working fluid stagnation points at each end of the heat pipe. Other configurations may also prove useful, such as heat pipes with multiple evaporators or multiple condensers. In such heat pipes, additional working fluid stagnation points form at locations dependent on the configuration of the thermal boundary conditions. These stagnation points divide the heat pipe into multiple cells that each have an evaporator and …

Experimental And Numerical Investigation Of Lauric Acid Melting At Suboptimal Inclines, Casey J. Troxler

Doctoral Dissertations and Master's Theses

Validation experiments are the baseline for completing numerical studies for engineering design. Applications of the enthalpy-porosity model have expanded in research with the growth of new technologies such as metal additive manufacturing or the renewed interest in thermal energy storage for supplementing renewable energy. A simplified experiment examining the melting behavior of lauric acid from an isothermal surface has become a common case for validating the performance of numerical models. Several studies of this rectangular experiment have been repeatedly used as model validation in a variety of problem conditions.

The first part of this study presents experimental data for the …

Deep Learning Strategies For Pool Boiling Heat Flux Prediction Using Image Sequences, Connor Heo

Graduate Theses and Dissertations

The understanding of bubble dynamics during boiling is critical to the design of advanced heater surfaces to improve the boiling heat transfer. The stochastic bubble nucleation, growth, and coalescence processes have made it challenging to obtain mechanistic models that can predict boiling heat flux based on the bubble dynamics. Traditional boiling image analysis relies on the extraction of the dominant physical quantities from the images and is thus limited to the existing knowledge of these quantities. Recently, machine-learning-aided analysis has shown success in boiling crisis detection, heat flux prediction, real-time image analysis, etc., whereas most of the existing studies are …

A Study Of The Efficiency And Effectiveness Of The First Four Iterations Of Sierpinski Carpet Fractal-Like Fins At Increasing Angles In Natural Convection, Sophia N. Fleri

Honors College Theses

Fractal geometries have been found in several studies to increase a fin’s thermal performance. Both the reductions of volume and mass accompanied by an increase in performance are desirable to prevent malfunction of the device through passive heat dissipation. The Sierpinski carpet fractal pattern, beginning with a basic square geometry in which an increasing number of perforations are incorporated through each successive iteration, reduces the fin’s mass while increasing its surface area simultaneously; this increase in surface area increases the rate of heat transfer experienced across the fin. The first four iterations of the Sierpinski carpet pattern, each with identical …

Emissivity Measurements Of Painted And Aerosol Deposited Thermographic Phosphors (Yag:Dy And Mfg:Mn), Wendy Flores-Brito

Mechanical Engineering ETDs

Combustion is one of the most difficult processes to model. Luminous flames are characteristically sooty, which creates a problem when modeling and calculating the combustion and heat transfer of the process; both of which are highly dependent on temperature and emissivity. Soot particle emissivity as well as gas contributions affect the heat transfer calculation and must be accounted for.

Thermographic phosphors (TP) are ceramic based phosphorescent materials that have a temperature dependent emission that can be exploited to obtain surface and gas temperature measurements, as well as 2D temperature maps. Emissivity knowledge is not needed to obtain temperature and is …

Efficient Enhancement Of Micro-Nucleation Rates In Flow-Boiling - By Concurrent Micro-Structuring Of The Boiling-Surface And Its Judicious Energization By Piezoelectric-Transducer Induced Acoustic Vibrations., Atharva Rahane

Dissertations, Master's Theses and Master's Reports

The report describes the science and technology backgrounds and uses for the technology breakthrough reported for enhanced flow-boiling based cooling of high-power density electronics (chips, memory etc.). A controlled but explosive growth in micro-scale nucleation rates during flow-boiling of HFE-7100 (electronics and environment friendly liquid from 3M, Inc) is enabled by the uses of inexpensive meshed-copper for micro-structuring of the boiling surface and a pair of Piezoelectric-transducers for active imposition of suitable acoustic vibrations. The pair of piezo transducers mounted just outside the mini-channel impose “in plane” acoustic vibrations of controllable amplitudes and frequencies, and they are used to induce …

Thermal Performance Of Sierpinski Carpet Fractal Fins At Various Angles Of Inclination In A Natural Convection Environment, Haidar Jamil Khalil

Electronic Theses and Dissertations

As technology advances, higher performance cooling systems are desired to meet numerous thermal management challenges. Extended surfaces, also known as heat sinks or fins, are commonly used to passively dissipate unwanted heat from mechanical and electrical systems. Fractal fins in accordance with the first four iterations (including a base iteration) of the Sierpinski carpet, manufactured from AL-5052, were studied along seven different inclinations from 0° (orientated perpendicular to the direction of gravity) to 90° (orientated parallel to the direction of gravity), in iterations of 15°. The purpose of study was to investigate the thermal performance of the first four fractal …

Surface Engineering Solutions For Immersion Phase Change Cooling Of Electronics, Brendon M. Doran

Master's Theses

Micro- and nano-scale surface modifications have been a subject of great interest for enhancing the pool boiling heat transfer performance of immersion cooling systems due to their ability to augment surface area, improve wickability, and increase nucleation site density. However, many of the surface modification technologies that have been previously demonstrated show a lack of evidence concerning scalability for use at an industrial level. In this work, the pool boiling heat transfer performance of nanoporous anodic aluminum oxide (AAO) films, copper oxide (CuO) nanostructure coatings, and 1D roll-molded microfin arrays has been studied. Each of these technologies possess scalability in …

Adding Semi-Structured Automated Grid Generation And The Menter-Shear Stress Turbulence Transport Model For Internal Combustion Engine Simulations To Novel Fem Lanl Combustion Codes, Brad Montgomery Philipbar

Mechanical Engineering ETDs

The addition of GridPro semi-structured, automated generation of grids for complex moving boundaries for combustion engine applications and the Menter Shear Stress Turbulent Transfer (SST) model are being developed by Los Alamos National Laboratory. The software is called Fast, Easy, Accurate, and Robust Continuum Engineering (FEARCE). In addition to improving the time and effort required to build complex grid geometry for turbulent reactive multi-phase flow in internal combustion engines, the SST turbulence model has been programmed into the Predictor Corrector Fractional-Step (PCS) Finite Element Method (FEM) for reactive flow and turbulent incompressible flow regime validation is performed. The Reynolds-Averaged Navier-Stokes …

Investigation Of Heat Exchanger Effectiveness Using A Surface Coating Technology, Allen Duffy

Graduate Theses, Dissertations, and Problem Reports

Diesel engine manufacturers continue to improve engine performance through increased thermal efficiency and reduced regulated emissions. The aftercooler located between the turbocharger air outlet and intake manifold experiences a wide range of operating conditions. Improving the heat transfer characteristics in the aftercooler can lead towards improved engine performance through increased charge air density. A surface coating has been proposed to enhance the heat transfer characteristics for a marine-based application on the water - side of the heat exchanger. To evaluate the efficacy of the coating, the rate of heat transfer with and without the coating was quantified in a controlled …

Laser Ablation Of Aluminum, Erika Nosal, Zachary Rahe, Arthur Pamboukis

Williams Honors College, Honors Research Projects

The laser ablation of metal carries relevance in a variety of engineering industries. This includes, but is not limited to, processes such as micromachining, or implementation on aircraft weaponry. The latter application is the reasoning for why aluminum is the specific metal in consideration, as it is commonly used for the construction of aircraft components.

The scope of this project was to optimize the energy dispersed through laser ablation on aluminum by mathematical modeling. The transient conduction process in the aluminum was modeled using a 2-dimensional cylindrical coordinate system in both MATLAB and ANSYS/Fluent. These models were adopted to simulate …

Experimental And Numerical Study Of The Stirling Engine Robust Foil Regenerator, Koji Yanaga

Graduate Theses, Dissertations, and Problem Reports

The regenerator is located between the heat accepter and the heat rejecter of the Stirling engine. It works as a thermal energy storage component in the engine. Most of the regenerators are made of woven screen or random fiber. However, the flow going through the woven screen or random fiber is similar to the cylinders in crossflow which has flow separation. To achieve higher engine efficiency, it is required to design a regenerator which has higher convective heat transfer, lower pressure drops. Therefore, a parallel channel regenerator called a robust foil regenerator was designed and manufactured.

In this study, a …

Thermal Modelling And Validation Of Heat Profiles In An Rf Plasma Micro-Thruster, Alec Sean Henken

Master's Theses

The need and demand for propulsion devices on nanosatellites has grown over the last decade due to interest in expanding nanosatellite mission abilities, such as attitude control, station-keeping, and collision avoidance. One potential micro-propulsion device suitable for nanosatellites is an electrothermal plasma thruster called Pocket Rocket. Pocket Rocket is a low-power, low-cost propulsion platform specifically designed for use in nanosatellites such as CubeSats. Due to difficulties associated with integrating propulsion devices onto spacecraft such as volume constraints and heat dissipation limitations, a characterization of the heat generation and heat transfer properties of Pocket Rocket is necessary. Several heat-transfer models of …

An Experimental Investigation Of The Cooling System For A Free Piston Stirling Engine, Akshay Milind Gupte

Graduate Theses, Dissertations, and Problem Reports

Free-Piston Stirling Engine (FPSE) has been identified as a good candidate for combined heat and power application (CHP). FPSE being highly efficient and environmentally friendly promises to facilitate the increasing demand in waste heat energy recovery systems. FPSE system consists of three important components: (1) hot side heat exchanger; (2) regenerator; and (3) cold side heat exchanger. The cold side heat exchanger is a crucial part as it enables to maintain an optimal temperature of the working fluid by rejecting heat.

This research contributes to the design of heat exchanger test rig and experimental measurement of cooling heat exchanger. The …

Design And Development Of Test Rigs To Experimentally Investigate Flow Loss And Heat Transfer In A Stirling Engine Heater Head, Pawan K. Yadav

Graduate Theses, Dissertations, and Problem Reports

The Stirling engines are attractive alternative for combined heat and power (CHP) systems, especially for high efficiency power generation using different heat sources. The hot side heat exchanger or heater head (HH) is one of the indispensable components of Stirling engines which transfers the heat from outside of the system into the working fluid. For development of a low cost, highly efficient and reliable CHP system, a novel HH has been designed and additively manufactured from Inconel 625. For the investigation of flow loss and heat transfer through this Stirling engine heater head, two benchtop test rigs were designed, developed, …

Multiphase Interaction In Low Density Volumetric Charring Ablators, Ali D. Omidy

Theses and Dissertations--Mechanical Engineering

The present thesis provides a description of historical and current modeling methods with recent discoveries within the ablation community. Several historical assumptions are challenged, namely the presence of water in Thermal Protection System (TPS) materials, presence of coking in TPS materials, non-uniform elemental production during pyrolysis reactions, and boundary layer gases, more specifically oxygen, interactions with the charred carbon interface.

The first topic assess the potential effect that water has when present within the ablator by examining the temperature prole histories of the recent flight case Mars Science Laboratory. The next topic uses experimental data to consider the instantaneous gas …

Natural Convection Heat Transfer Of Inclined Sierpinski Carpet Fractal Fins, Luke A. Fussell

Electronic Theses and Dissertations

When designing extended surfaces for the thermal management of electronic devices in aerospace applications it is critically important to minimize mass. However, this can be difficult to achieve as the rate of heat dissipated is directly proportional to the surface area. Fortunately, when certain fractal geometries, like the Sierpinski carpet, are utilized in the design of extended surfaces an increase in surface area and simultaneous decrease in mass can be achieved. The thermal performance of fins inspired by the first four fractal iterations of the Sierpinski carpet pattern was experimentally examined in a natural convection environment. The fractal fins were …

Effects Of Ultrasonic Transducers On Heat Transfer In Packed Particle Beds, David Patrick Moseley

Masters Theses

The objective of this study was to determine the effects of ultrasonic transducers on heat transfer in a packed particle bed heat exchanger. Although substantial research has been devoted to ultrasound, and the associated improvements in heat transfer, data regarding the effects on packed particle beds is non-existent. This is of particular interest given the potential to improve heat transfer in a wide variety of packed particle bed systems. A 42.9% increase in the heat transfer rate was demonstrated as the result of improved fluid convection throughout the packed particle bed. Secondary effects, including acoustic cavitation, acoustic streaming and local …

Me 350 Air Conditioning Experiment, Joshua Baida, Ellie Hallner, Tyler Eschenbach

Mechanical Engineering

In keeping with Cal Poly's focus on physically applying the concepts learned in the classroom, our team of engineering students has compiled a laboratory experiment displaying the basic thermodynamic cycle found in air conditioning systems. This vapor compression cycle is displayed on a visualization board that features all four major components of the system: the compressor, the evaporator, the condenser, and the throttling valve. Students will take measurements of temperature and pressure at each stage in the cycle and also gauge the power draw from the compressor to gain an understanding of how performance and electricity cost come into play …

Efficiency Testing Of An Electronic Speed Controller, Grace Cowell, Matthew Hudson, Marcus Pereira

Mechanical Engineering

This project required the development of a rig that could experimentally determine the efficiency of an Electronic Speed Controller (ESC). The selected design focuses on measuring the losses due to heat from the device and comparing this to its input power. The selected design is a flow rig that utilizes the heat equation q=ṁcpΔT. The rig provides a steady state measurement of the ESC heat output by passing a known mass flow rate of air across the ESC and measuring the temperature difference. It uses a flowmeter to determine ṁ, thermocouples to determine ΔT, and a table lookup to determine …

Design Of The University Of Akron's 2015 Fsae Electric Vehicle Braking System, Nicholas D. Galbincea

Williams Honors College, Honors Research Projects

The following report encompasses the design of the 2015 University of Akron’s FSAE formula electric braking system. The system is one based on hydraulic braking and designed for a one man performance racing vehicle. The objective of the system is to convert the kinetic energy of the vehicle into thermal energy, allowing the vehicle to decelerate optimally and safely. The design includes three major categories: calculation and evaluation of the hydraulic system in order to select calipers and master cylinders, the design of the pedal box, and the design of the rotors.

The results and findings of the proceeding report …

Lightweight, High-Temperature Radiator For In-Space Nuclear-Electric Power And Propulsion, Briana N. Tomboulian

Doctoral Dissertations

The desire to explore deep space destinations with high-power and high-speed spacecraft inspired this work. Nuclear Electric Propulsion (NEP), shown to provide orders of magnitude higher specific impulse and propulsion efficiency over traditional chemical rockets, has been identified as an enabling technology for this goal. One of large obstacle to launching an NEP vehicle is total mass. Increasing the specific power (kW/kg) of the heat radiator component is necessary to meet NASA’s mass targets. This work evaluated a novel lightweight, high-temperature carbon fiber radiator designed to meet the mass requirements of future NEP missions. The research is grouped into three …

A Metrics-Based Sustainability Assessment Of Cryogenic Machining Using Modeling And Optimization Of Process Performance, Tao Lu

Theses and Dissertations--Mechanical Engineering

The development of a sustainable manufacturing process requires a comprehensive evaluation method and fundamental understanding of the processes. Coolant application is a critical sustainability concern in the widely used machining process. Cryogenic machining is considered a candidate for sustainable coolant application. However, the lack of comprehensive evaluation methods leaves significant uncertainties about the overall sustainability performance of cryogenic machining. Also, the lack of practical application guidelines based on scientific understanding of the heat transfer mechanism in cryogenic machining limits the process optimization from achieving the most sustainable performance.

In this dissertation, based on a proposed Process Sustainability Index (ProcSI …

Characterization Of Heat Transfer Coefficient Uncertainty In Support Of High Temperature Probe Measurement Technology, Marcus S. Conner

Masters Theses

The development of new materials and processes have enabled defense, industrial, and research devices that operate in high temperature environments. Measurement technology must keep up with the demand of these environments.

The objective of this work is to provide a correlation between the heat transfer coefficient (and Nusselt Number) and the flow Reynolds number (and Prandtl number) for a truncated cylindrical probe. The correlation provides reduced uncertainty for materials whose heat transfer coefficient is not well defined. The configuration for the experiment uses the University of Tennessee Space Institute’s (UTSI) blow down air supply system discharging into a duct and …

Investigation Of The One-Probe And Two-Probe Calibration Integral Equation Methods Using Experimental Data, Abhay Sanjeev Pande

Masters Theses

This work aims to expand the applicability of the recently devised physics-based Calibration Integral Equation Method (CIEM) at the University of Tennessee Knoxville, for solving the Inverse Heat Conduction Problem (IHCP) as applied to a one-dimensional domain. Contrary to conventional schemes of solving the IHCP, the CIEM does not require the knowledge of the thermo-physical properties of the domain, sensor characterization and sensor probe locations. The pertinent information is implicitly accounted for via an experimental run. The experimental run ‘calibrates’ the physics of the domain and is called the ‘calibration run’. The net surface heat flux during a real ‘unknown’ …

Analysis And Testing Of Heat Transfer Through Honeycomb Panels, Daniel D. Nguyen

Aerospace Engineering

This project attempts to simulate accurately the thermal conductivity of honeycomb panels in the normal direction. Due to the large empty space of the honeycomb core, the thermal radiation mode of heat transfer was modeled along with conduction. Using Newton’s Method to solve for a steady state model of heat moving through the honeycomb panel, the theoretical effective thermal conduction of the honeycomb panel was found, ranging from 1.03 to 1.07 Q/m/K for a heat input of 2.5 W to 11.8 W. An experimental model was designed to test the theoretical results, using a cold plate and a heat plate …