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Articles 1 - 30 of 35
Full-Text Articles in Heat Transfer, Combustion
Experimental Characterization Of An Additively Manufactured Porous Gyroid Air-Cooled Heat Sink, Grant S. Resler
Experimental Characterization Of An Additively Manufactured Porous Gyroid Air-Cooled Heat Sink, Grant S. Resler
Mechanical Engineering Undergraduate Honors Theses
This paper presents the development of a ducted test facility designed to evaluate heat sinks efficiency at varying air velocities. This enables the evaluation of both heat transfer and pressure drop performance. These metrics are essential to the overall efficiency of heat sinks and help identify the optimal air velocity to achieve the desired thermal performance. A standard plate fin heat sink was used as a control for comparison to a novel heat sink. The specialized heat sink geometry was generated using nTop, a generative design software focused on additive manufacturing. This design was fabricated via Direct Metal Laser Sintering …
Effects Of Thermal Interface Materials On Thermal Conductivity Measurement Using A Modified Astm D5470 Thermal Resistance Tester, Chinmaya Joshi
Effects Of Thermal Interface Materials On Thermal Conductivity Measurement Using A Modified Astm D5470 Thermal Resistance Tester, Chinmaya Joshi
Mechanical Engineering Undergraduate Honors Theses
In this paper, we have investigated the effect of thermal interface materials (TIMs) on the accuracy and uncertainty of thermal conductivity measurements. A modified ASTM D5470 thermal resistance tester (TRT) is developed to measure the out-of-plane thermal conductivity of pyrolytic graphite (PG) and grade 2 titanium (TiG2) with and without TIMs. Compared to the ASTM D5470 standard, this modified design uses three thermocouples per side to support regressive analysis and explores the use of TIMs.s Nine PG samples and four TiG2 samples of varying thickness have been tested to obtain thermal resistance as a function of sample thickness. The steady-state …
Validating An Electronics Cooler Experiment And Optimizing Its Performance Using Ansys Icepak, Daniel V. Curl
Validating An Electronics Cooler Experiment And Optimizing Its Performance Using Ansys Icepak, Daniel V. Curl
Mechanical Engineering Undergraduate Honors Theses
Researchers at the University of Arkansas' Mechanical and Electrical Engineering Research Departments have designed and built a cold plate and substrate design for a 10 kV SiC MOSFET power module. Many variables define the design of the cold plate and substrate system and have quantifiable effects on the device’s performance. These variables include but are not limited to geometry and material selection of the fins and substrate. Manufacturing many test designs, running experiments, and comparing their performance is a time-consuming and expensive design optimization method that may be effective for some low-cost applications. Still, simulation is often a more cost-effective …
Introduction To Building Energy Modeling And Analysis Using Energyplus, Jackson C. Burnett
Introduction To Building Energy Modeling And Analysis Using Energyplus, Jackson C. Burnett
Mechanical Engineering Undergraduate Honors Theses
Retail stores are dynamic environments where human activities significantly influence energy consumption patterns, particularly affecting heating, ventilation, and air conditioning (HVAC) demands. Existing energy models, such as those developed using EnergyPlus, often rely on generalized assumptions about human occupancy and behavior, leading to discrepancies between predicted and actual energy usage. This research aimed to enhance the accuracy of energy modeling for retail stores by conducting a sensitivity analysis of occupancy using EnergyPlus simulations. The study investigated how variations in occupancy levels impact HVAC loads, cooling and heating demands, and overall energy use. Results showed that increasing occupancy leads to higher …
Development Of A Manifold Microchannel Heat Sink For The Electrification Of Aircraft, Joshua Mora Sanchez
Development Of A Manifold Microchannel Heat Sink For The Electrification Of Aircraft, Joshua Mora Sanchez
Mechanical Engineering Undergraduate Honors Theses
The miniaturization of microprocessors and power electronics is leading to critical thermal management challenges. For instance, the heat flux generated in modern computer chips is at the order of 100W/cm², which is well beyond the limit of air cooling. This high heat generation can cause a variety of thermal or mechanical failures in electronic devices. As such, there is a pressing need to devise effective cooling strategies for these microelectronic devices. Liquid cooling with microchannel heat sinks is a promising technology for high power loads. Nevertheless, traditional heat sinks with straight microchannels suffer from two critical challenges: high pressure drop …
Experimental And Numerical Investigation Of Air-Cooled Heat Sinks, Ethan Weems
Experimental And Numerical Investigation Of Air-Cooled Heat Sinks, Ethan Weems
Mechanical Engineering Undergraduate Honors Theses
Lightweight and affordable cooling capabilities are critical as the physical scale of electronics continues to decrease. Air-cooled heat sinks that dissipate heat from electronic components to the surrounding air are excellent candidates to fill this role. While plate-fin and pin-fin heat sinks have been implemented extensively for electronic cooling, recent advances in additive manufacturing enable the fabrication of more complex structures. In this undergraduate Honors thesis, a means by which to generate novel heat sink geometries is presented. To that end, an experimental characterization facility is developed to evaluate existing traditional heat sinks. The heat transfer performance of the heat …
Capabilities Of Sintered Silver As A High Temperature Packaging Material, Bakhtiyar Mohammad Nafis
Capabilities Of Sintered Silver As A High Temperature Packaging Material, Bakhtiyar Mohammad Nafis
Graduate Theses and Dissertations
With electrification progressing across many sectors including industry, automotive and aerospace, the power density requirements are changing. The increased power density results in higher and higher ambient temperatures that electronics are exposed to. The response has been to move towards wide bandgap (WBG) semiconductor devices that can withstand much greater temperatures and can operate at much higher voltages than silicon. Additionally, these WBG devices deliver low drain-source on resistance (RDS_on) capabilities, enabling high current power modules that increase power density even further. This also requires the packaging to evolve in order to withstand the new requirements. As a result, researchers …
Thermal Resistance Characterization Of High-Voltage Sic Power Module, Landon Lemmons
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 …
Advanced Jet Impingement Cooling For Power Electronics, Reece Whitt
Advanced Jet Impingement Cooling For Power Electronics, Reece Whitt
Graduate Theses and Dissertations
Convective heat transfer by jet impingement cooling offers a suitable solution for high heat flux applications. Compared to techniques that rely on bulk conduction in series with convection, direct liquid impingement reduces the thermal resistance between power device hot spots and the coolant. Using additive manufacturing processes, location specific jets can be integrated into high voltage power electronics systems. Custom manifolds can be designed to reduce pressure drop, while simultaneously fine-tuning the thermal management efficiency. Although capable of highly efficient cooling, static impingement devices must be designed for the worst-case cooling requirements for a transient power profile, possibly resulting in …
A Review Of Nano And Microscale Heat Transfer: An Experimental And Molecular Dynamics Perspective, Samyabrata Chatterjee, Paras, Han Hu, Monojit Chakraborty
A Review Of Nano And Microscale Heat Transfer: An Experimental And Molecular Dynamics Perspective, Samyabrata Chatterjee, Paras, Han Hu, Monojit Chakraborty
Mechanical Engineering Faculty Publications and Presentations
Significant progress in the development of micro and nanoscale devices has been observed for the past three decades. The thermal transportation in these small-length scales varies significantly, and it is difficult to explain the underlying physics using the pre-existing theoretical formulations. When the bulk dimension of a system is comparable to or smaller than the mean free path (MFP) of the thermal carriers, classical theories, such as Fourier’s Law of heat conduction, are unable to accurately explain the system energy dynamics. The phenomena of energy transit and conversion at the micro to nanoscale is an interesting topic of research due …
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 …
Reynolds-Averaged Navier-Stokes Cfd Simulation Of High-Speed Boundary Layers, Michael Tullis
Reynolds-Averaged Navier-Stokes Cfd Simulation Of High-Speed Boundary Layers, Michael Tullis
Mechanical Engineering Undergraduate Honors Theses
This paper presents an investigation of Reynolds-averaged Navier-Stokes (RANS) turbulence models used in computational fluid dynamics (CFD) simulations of boundary layer flow and heat transfer in high Mach number flows. This study evaluates an industry standard RANS turbulence model (k-omega SST) and a recently proposed modification to that model (Danis and Durbin [1]), and quantifies the accuracy for predicting high Mach number boundary layer flow. The test cases were previously documented by Duan et al. (2018), who used direct numerical simulation (DNS) to calculate boundary layer flow of an ideal gas over a flat plate at freestream Mach numbers ranging …
Development Of An Accelerated Life Testing Method For Reliability Assessment Of Wire Bonded Interconnects Subjected To Mechanical And Electromigratory Stresses, Whit Vinson
Graduate Theses and Dissertations
Power electronic advancement trends indicate that device power density will continue to increase as a result of increased power requirements and desired device form factor reduction in order to reduce weight and material costs and increase ease of integration into next-generation power systems. With these advancements come concerns regarding device reliability. The compounded effects of increased power density and form factor reduction in electrical conductors will yield amplified joule heating effects in addition to the already increasing device temperature profiles resulting from the incorporation of wide bandgap technology into power systems. Joule heating effects can lead to a variety of …
Generative Designs Of Lightweight Air-Cooled Heat Exchangers, Connor Miller
Generative Designs Of Lightweight Air-Cooled Heat Exchangers, Connor Miller
Mechanical Engineering Undergraduate Honors Theses
The development of high-performance air-cooled heat exchangers is required to permit the rapid growth of vehicle and aircraft electrification. In electric vehicles and airliners, the motors and power electronics are integrated into a compact space, leading to unprecedently high power density. To achieve higher overall thermal efficiency, the heat exchangers must be extremely light while maintaining their heat transfer performance and mechanical robustness. Recently advances in 3D metal printing, e.g., direct metal laser sintering, and selective laser melting, have enabled the manufacturing of high-performance robust heat exchangers by eliminating thermal boundary resistance and ensuring a uniform thermal expansion coefficient. Nonetheless, …
Durability Of Non-Metallic Materials For Additively Manufactured Heat Spreader Fabrication, Rafael Estrella
Durability Of Non-Metallic Materials For Additively Manufactured Heat Spreader Fabrication, Rafael Estrella
Mechanical Engineering Undergraduate Honors Theses
Power electronics are necessary to convert power from DC sources for AC applications. As this technology trends toward smaller packaging for denser power loads, the increased electrical losses result in deleterious excess heat. Thermal management devices are required to prevent the effects of thermal runaway from shortening the longevity of these modules. Nonmetallic jet impingement heat spreaders provide several benefits in terms of weight and performance over conventional cold plates while not accentuating EMI from the switches in the power module; however, the polymer makeup of the materials previously used for fabricating these devices raises durability concerns under the high …
Deep Learning Strategies For Pool Boiling Heat Flux Prediction Using Image Sequences, Connor Heo
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 …
Thermometry Via Diffusion In Ferrous Core-Shell Nanoparticles For Induction Heating Applications, Hayden Carlton
Thermometry Via Diffusion In Ferrous Core-Shell Nanoparticles For Induction Heating Applications, Hayden Carlton
Graduate Theses and Dissertations
Induction heating causes the release of enormous amounts of heat from dispersed magnetic nanoparticles. While the rate of heat transfer can be easily quantified calorimetrically, measuring the temperature of the nanoparticles on the nanoscale presents experimental challenges. Fully characterizing the temperature and thermal output of these magnetic particles is necessary to gauge overall heating efficiency and to provide a more holistic understanding of heat transfer on the nanoscale. Herein, this dissertation seeks to develop a novel nanoparticle thermometry technique, which correlates diffusion behavior in core-shell nanoparticles to local temperature. Initial measurements suggested that heating silica capped ferrous nanoparticles (SCNPs) via …
Transient Performance And Melt Front Characterization Of Phase Change Materials, Tyler Stamps
Transient Performance And Melt Front Characterization Of Phase Change Materials, Tyler Stamps
Mechanical Engineering Undergraduate Honors Theses
Thermal management systems are often over-designed for average use in order to handle spikes in heat generation, which increases the spatial and financial requirements. One way to mitigate this is via the use of phase change materials (PCMs) as thermal buffers and storage media. This material type exhibits excellent latent heat at the sacrifice of conductivity. The present paper examines the melt front behavior of a common solid to liquid PCM, paraffin, experimentally and numerically. The experimental scenario was a block of PCM with a constant temperature heat flux introduced on one end and a constant temperature cold boundary condition …
Algorithm Development Of Topology Optimization For Pcm Based Heat Sinks, Diego L. De Los Reyes
Algorithm Development Of Topology Optimization For Pcm Based Heat Sinks, Diego L. De Los Reyes
Mechanical Engineering Undergraduate Honors Theses
With the inherent usage of the computer when dealing with additive manufacturing, it only makes sense to use that higher computing power through simulation and iterative design to use the mathematical concept of topology and optimize the kind of geometry and shapes to be produced for a certain application, especially thermal ones since most 3D printing applications focus on purely the mechanical. To determine what the shape will be, an objective function of how much heat can be dispersed from a hypothetical heat source, assumed to be a type of electronic device, is maximized while being constrained by other variables, …
Thermal Testing And Characterization Of Nanoparticles Synthesized For Biological Treatment, Tonie Butler
Thermal Testing And Characterization Of Nanoparticles Synthesized For Biological Treatment, Tonie Butler
Mechanical Engineering Undergraduate Honors Theses
The overall goal of this research project is to synthesize iron core, silica capped nanoparticles that, when they are exposed to a particular magnetic field, will react by increasing in temperature and emitting substantial thermal output. They will be injected into the human body for biological benefit by targeted thermal radiation. Once in the human body, ideally, they will be able to target a specific area, and then a magnetic field will be applied to induce thermal output through the process of hyperthermia. As the nanoparticles emit heat, they will mimic the natural bodily behavior seen by way of hyperthermia, …
What Difference Does A Catalyst Make?, Tammy Guthrie, Mike Jackson, Holly Haney
What Difference Does A Catalyst Make?, Tammy Guthrie, Mike Jackson, Holly Haney
High School Lesson Plans
Students will use different catalysts for the decomposition of Hydrogen Peroxide, to determine if different catalysts affect the energy that is generated during the reaction.
Enhancement Of Phase Change Material Sorbitol By Nanoparticle Inclusion For Improving Thermal Energy Storage Capabilities, Joshua Kasitz
Enhancement Of Phase Change Material Sorbitol By Nanoparticle Inclusion For Improving Thermal Energy Storage Capabilities, Joshua Kasitz
Mechanical Engineering Undergraduate Honors Theses
Thermal management of electronic devices has become an increasingly vital field of study with the rapid miniaturization of many key electrical components. With the significant improvement of semiconductor manufacturing and intensified focus on interconnects, electronic devices have decreased in size at an incredible rate. Decreasing spatial requirements is essential to improving device capabilities as the electronic system is able to incorporate more components. Currently, electronic systems are drastically limited by the capabilities of their cooling mechanisms. Smaller devices lead to large increases in the energy density of the system and require more powerful cooling systems to maintain proper component operating …
Energy Transformation And Conservation Investigation, Mike Jackson, Holly Haney
Energy Transformation And Conservation Investigation, Mike Jackson, Holly Haney
High School Lesson Plans
Students will use a thermoelectric generator module to analyze the relationship between thermal and electrical energies. Using data collection sensors and analysis software, students will investigate the relationship between the temperature gradient across a thermoelectric generator module and the resulting electrical potential. Students will then use their data and analysis to solve problems relating to waste thermal energy in electrical systems and communicate their work to their peers and teacher.
Optimization Of The Practice Of Slow Cooling Steel Bars: A Redesign And Modernization Of Materials, Eryn Johnston
Optimization Of The Practice Of Slow Cooling Steel Bars: A Redesign And Modernization Of Materials, Eryn Johnston
Mechanical Engineering Undergraduate Honors Theses
Throughout the process of steel making, certain grades of steel are a higher risk for defects caused by the inability to quickly diffuse hydrogen through the steel when cooled to room temperature at a normal rate based on the ambient air temperature. To reduce the hydrogen flaking defects that are caused due to hydrogen entrapment in the steel, the process of slow cooling is utilized. This process reduces the cooling rate of steel bars by keeping them at a higher temperature for extended periods and in turn gives the hydrogen a chance to fully dissipate from the steel. In many …
What Can I Do As A Student To Make A Positive Impact On The Environment?, Tammy Guthrie, Greg Herzig, Kathy Prophet, Cassie Kautzer
What Can I Do As A Student To Make A Positive Impact On The Environment?, Tammy Guthrie, Greg Herzig, Kathy Prophet, Cassie Kautzer
Middle School Lesson Plans
Students discover ways they can make a positive impact on the environment.
Energy From Chemical Reactions: Understanding The Combustion Engine, Tammy Guthrie, Kathy Prophet, Greg Herzig, Cassie Kautzer
Energy From Chemical Reactions: Understanding The Combustion Engine, Tammy Guthrie, Kathy Prophet, Greg Herzig, Cassie Kautzer
Middle School Lesson Plans
Automobiles produce a large amount of heat generated by the burning of gasoline. Burning gasoline is a chemical reaction that causes a phase change. This is called combustible energy. During combustion fuel combines with oxygen to release energy (such as heat, light, sound) along with another product that is often considered waste. Most of the energy produced is not used to power the automobile, but is released as heat. 19.3 pounds of the greenhouse gas, carbon dioxide, is produced from the combustion of 1 gallon of U.S. gasoline according to the U.S. Energy Information Administration.
Computer Simulation Of Pore Migration Due To Temperature Gradients In Nuclear Oxide Fuel, Ian Wayne Vance
Computer Simulation Of Pore Migration Due To Temperature Gradients In Nuclear Oxide Fuel, Ian Wayne Vance
Graduate Theses and Dissertations
A phase-field simulation model is being presented that captures the thermal-gradient-driven migration of pores in oxide fuel associated with fuel restructuring. The model utilizes a Cahn-Hilliard equation supplemented with an advection term to describe the vapor transport of fuel material through the pore interior due to gradients in vapor pressure. In addition, the model also captures changes in a migrating pores’ morphology. Simulations demonstrate that the model successfully predicts pore migration towards the hottest portion of the fuel, the centerline. The simulations also demonstrate changes in pore shape that are in agreement with previous experimental observations. Initially isotropic pores are …
Characterization Of Plastic Deformation Evolution In Single Crystal And Nanocrystalline Cu During Shock By Atomistic Simulations, Mehrdad Mirzaei Sichani
Characterization Of Plastic Deformation Evolution In Single Crystal And Nanocrystalline Cu During Shock By Atomistic Simulations, Mehrdad Mirzaei Sichani
Graduate Theses and Dissertations
The objective of this dissertation is to characterize the evolution of plastic deformation mechanisms in single crystal and nanocrystalline Cu models during shock by atomistic simulations. Molecular dynamics (MD) simulations are performed for a range of particle velocities from 0.5 to 1.7 km/s and initial temperatures of 5, 300 and 600 K for single crystal models as well as particle velocities from 1.5 to 3.4 km/s for nanocrystalline models with grain diameters of 6, 11, 16 and 26 nm. For single crystal models, four different shock directions are selected, <100>, <110>, <111> and <321>, and dislocation density behind the shock wave …
Go With The Flow –Thermoelectric Energy, Shawn Bell
Go With The Flow –Thermoelectric Energy, Shawn Bell
Middle School Lesson Plans
In this unit, students will learn how thermal energy be transferred and transformed. They will carry out investigations to gather evidence to support an explanation about direct conversion of heat into electrical energy. They will develop a model that shows the components of the system and changes in the system being investigated, and they will use evidence from the investigation to construct an explanation for how the energy flows.
Modeling Radiation Heat Transfer For Building’S Cooling And Heating Loads: Considering The Role Of Clear, Cloudy, And Dusty Conditions In Hot And Dry Climates, Salem Ahmed Algarni
Modeling Radiation Heat Transfer For Building’S Cooling And Heating Loads: Considering The Role Of Clear, Cloudy, And Dusty Conditions In Hot And Dry Climates, Salem Ahmed Algarni
Graduate Theses and Dissertations
The influence of transient factors such as sky long wave radiation exchange and atmospheric aerosols (i.e., smog, and dust – made up of sand, clay, and silt) are not carefully considered in current building design and simulation models. Therefore, the research objective was to better understand and account for such variables, resulting in improved radiative predictive capabilities, especially important for hot and dry climates under different sky conditions including clean, cloudy, and dusty. Overall, results of this dissertation provided a better prediction method for sky long wave radiation exchange with a building’s roof and the impact of dust accumulation on …