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Full-Text Articles in Engineering
Thermal Atomization On Superhydrophobic Surfaces Of Varying Temperature Jump Length, Eric D. Lee, Daniel Maynes, Julie Crockett, Brian D. Iverson
Thermal Atomization On Superhydrophobic Surfaces Of Varying Temperature Jump Length, Eric D. Lee, Daniel Maynes, Julie Crockett, Brian D. Iverson
Faculty Publications
This paper presents an experimental study of drop impingement and thermal atomization on hydrophobic and superhydrophobic (SH) surfaces. Superhydrophobic surfaces having both microscale and nanoscale geometry are considered. Microscale SH surfaces are coated with a hydrophobic coating and exhibit micropillars and cavities which are classified using the surface solid fraction and center to center pitch. The solid fraction and pitch values explored in this study range from 0.05-1.0 and 8-60 μm respectively. Nanoscale textured surfaces are created by applying a blanket layer of carbon nanotubes. Both types of surfaces are further classified by a temperature jump length (λ …
Heat Transfer To Rolling Or Sliding Drops On Inclined Heated Superhydrophobic Surfaces, Joseph Merkley Furner
Heat Transfer To Rolling Or Sliding Drops On Inclined Heated Superhydrophobic Surfaces, Joseph Merkley Furner
Theses and Dissertations
This thesis examines the time resolved heat transfer to drops rolling or sliding along inclined, subcritical heated non-wetting surfaces. Results were experimentally obtained using IR imaging for a smooth hydrophobic surface and post as well as rib structured superhydrophobic surfaces of varying solid fraction (f_s = 0.06 - 0.5). Tests were performed at varying inclination angle (α = 10, 15, 20, and 25°), drop volume (12, 20, 30, and 40 μL), and surface temperature (T_w = 50, 65, and 80 °C). Rib structured superhydrophobic surfaces were explored for drops moving parallel and perpendicular to the rib structures. The findings indicate …
Thermal Atomization Of Impinging Drops On Superheated Superhydrophobic Surfaces, Eric Lee
Thermal Atomization Of Impinging Drops On Superheated Superhydrophobic Surfaces, Eric Lee
Theses and Dissertations
Drop impact on a surface has an effect on nearly every industry and this impact may have adverse effects if not controlled. Superhydrophobic (SH) surfaces have been created with the extreme ability to repel water. These surfaces exist in nature but may also be fabricated using modern techniques. This thesis explores heat transfer from these SH surfaces to drops impacting them. This thesis is devoted to increasing the breadth of knowledge of thermal atomization during drop impingement on superheated SH surfaces. When a water drop impinges vertically on a horizontal superheated surface, intense atomization can occur. The atomization is caused …
Thermal Transport To Impinging Droplets On Superhydrophobic Surfaces, Jonathan C. Burnett
Thermal Transport To Impinging Droplets On Superhydrophobic Surfaces, Jonathan C. Burnett
Theses and Dissertations
An analytical model is developed to quantify the heat transfer to droplets impinging on heated superhydrophobic (SH) surfaces. Integral analysis is used to incorporate an apparent temperature jump at the superhydrophobic surface as a boundary condition. This Thesis considers the scenario of both isotropic and anisotropic slip, as would be realized on post-cavity style and rib-cavity style SH surfaces. This thermal model is combined with a hydrodynamic model which incorporates velocity slip at the surface. Use of the two models allows determination of the overall cooling effectiveness, a metric outlined in contemporary work. The effect of varying velocity slip and …
Jet Impingement Heat Transfer From Superheated, Superhydrophobic Surfaces, David Jacob Butterfield
Jet Impingement Heat Transfer From Superheated, Superhydrophobic Surfaces, David Jacob Butterfield
Theses and Dissertations
Liquid jet impingement is a technique ubiquitously used to rapidly remove large amounts of heat from a surface. Several different regions of heat transfer spanning from forced convection to nucleate, transition, and film boiling can occur very near to one other both temporally and spatially in quenching or high wall heat flux scenarios. Heat transfer involving jet impingement has previously shown dependency both on jet characteristics such as flow rate and temperature as well as surface material properties. Water droplets are known to bead up upon contact with superhydrophobic (SH) surfaces. This is due to reduced surface attraction caused by …
Thermal Atomization Due To Boiling During Droplet Impingement On Superhydrophobic Surfaces, Preston Todd Emerson
Thermal Atomization Due To Boiling During Droplet Impingement On Superhydrophobic Surfaces, Preston Todd Emerson
Theses and Dissertations
Superhydrophobic (SH) surfaces are characterized by their extraordinary water repellent qualities. When water comes in contact with these surfaces, it beads up and rolls around. This phenomenon is due partially to surface chemistry which promotes weak adhesive forces between liquid and solid. However, micro- and nanoscale surface roughness also plays a crucial role by trapping air beneath the liquid, reducing liquid-solid contact. Many advantages of these surfaces have been identified, including drag reduction and self-cleaning properties, and the body of research regarding them has grown rapidly over the past few decades.This thesis is concerned with water droplets impinging superheated, superhydrophobic …
Influence Of Micro-Structured Superhydrophobic Surfaces On Nucleation And Natural Convection In A Heated Pool, Adam Cowley, Daniel Maynes, Julie Crockett, Brian D. Iverson
Influence Of Micro-Structured Superhydrophobic Surfaces On Nucleation And Natural Convection In A Heated Pool, Adam Cowley, Daniel Maynes, Julie Crockett, Brian D. Iverson
Faculty Publications
This word experimentally explores sub-boiling pool nucleation on micro-structured superhydrophobic surfaces. All surfaces tested were submerged in a 20 mm deep pool of water and heated from below to maintain a constant surface temperature, while the side walls of the pool were insulated, and the top was covered. Three thermocouples positioned in the pool obtain the average pool temperature. A heat flux sensor is placed directly beneath the surface to measure the heat flux supplied to the pool. Free convection heat transfer coefficients are obtained for the sub-boiling temperature range of 40 – 90 ºC. Six surface types are studied: …
Characterization Of Pyrolysis Products From Fast Pyrolysis Of Live And Dead Vegetation, Mohammad Saeed Safdari
Characterization Of Pyrolysis Products From Fast Pyrolysis Of Live And Dead Vegetation, Mohammad Saeed Safdari
Theses and Dissertations
Wildland fire, which includes both planned (prescribed fire) and unplanned (wildfire) fires, is an important component of many ecosystems. Prescribed burning (controlled burning) is used as an effective tool in managing a variety of ecosystems in the United States to reduce accumulation of hazardous fuels, manage wildlife habitats, mimic natural fire occurrence, manage traditional native foods, and provide other ecological and societal benefits. During wildland fires, both live and dead (biomass) plants undergo a two-step thermal degradation process (pyrolysis and combustion) when exposed to high temperatures. Pyrolysis is the thermal decomposition of organic material, which does not require the presence …
Bubble Nucleation In Superhydrophobic Microchannels Due To Subcritical Heating, Adam Cowley, Daniel Maynes, Julie Crockett, Brian D. Iverson
Bubble Nucleation In Superhydrophobic Microchannels Due To Subcritical Heating, Adam Cowley, Daniel Maynes, Julie Crockett, Brian D. Iverson
Faculty Publications
This work experimentally studies the effects of single wall heating on laminar flow in a high-aspect ratio superhydrophobic microchannel. When water that is saturated with air is used as the working liquid, the non-wetted cavities on the superhydrophobic surfaces act as nucleation sites and allow air to effervesce out of the water and onto the surface when heated. Previous works in the literature have only considered the opposite case where the water is undersaturated and absorbs air out the cavities for a microchannel setting. The microchannel considered in this work consists of a rib/cavity structured superhydrophobic surface and a glass …
Design And Analysis Of Compressed Air Power Harvesting Systems, Zachary James Sadler
Design And Analysis Of Compressed Air Power Harvesting Systems, Zachary James Sadler
Theses and Dissertations
Procedure for site discovery, system design, and optimization of power harvesting systems is developed with an emphasis on application to air compressors. Limitations for the usage of infrared pyrometers is evaluated. A system of governing equations for thermoelectric generators is developed. A solution method for solving the system of equations is created in order to predict power output from the device. Payback analysis is proposed for determining economic viability. A genetic algorithm is used to optimize the power harvesting system payback with changing quantities and varieties of thermoelectric generators, as well as the back work put into cooling the thermoelectric …
Design And Analysis Of Compressed Air Power Harvesting Systems, Zachary James Sadler
Design And Analysis Of Compressed Air Power Harvesting Systems, Zachary James Sadler
Theses and Dissertations
Procedure for site discovery, system design, and optimization of power harvesting systems is developed with an emphasis on application to air compressors. Limitations for the usage of infrared pyrometers is evaluated. A system of governing equations for thermoelectric generators is developed. A solution method for solving the system of equations is created in order to predict power output from the device. Payback analysis is proposed for determining economic viability. A genetic algorithm is used to optimize the power harvesting system payback with changing quantities and varieties of thermoelectric generators, as well as the back work put into cooling the thermoelectric …
Hydrodynamic And Thermal Effects Of Sub-Critical Heating On Superhydrophobic Surfaces And Microchannels, Adam M. Cowley
Hydrodynamic And Thermal Effects Of Sub-Critical Heating On Superhydrophobic Surfaces And Microchannels, Adam M. Cowley
Theses and Dissertations
This dissertation focuses on the effects of heating on superhydrophobic (SHPo) surfaces. The work is divided into two main categories: heat transfer without mass transfer and heat transfer in conjunction with mass transfer. Numerical methods are used to explore the prior while experimental methods are utilized for the latter. The numerical work explores convective heat transfer in SHPo parallel plate microchannels and is separated into two stand-alone chapters that have been published archivally. The first considers surfaces with a rib/cavity structure and the second considers surfaces patterned with a square lattice of square posts. Laminar, fully developed, steady flow with …
Origami: Numerical Solutions Of Apparent Absorptivity In Origami Folds, Michael Farnsworth, Brian Iverson
Origami: Numerical Solutions Of Apparent Absorptivity In Origami Folds, Michael Farnsworth, Brian Iverson
Journal of Undergraduate Research
There are three major types of heat transfer: conduction, convection, and radiation. In many cases, radiation is ignored due to the fact that the amount of heat transferred by this method tend to be small compared to conduction and convection. However, in space and in some settings on earth, radiation is dominant and important. Absorptivity is a measure of an object’s ability to absorb radiation, and apparent absorptivity is a measure of how the shape of an object affects the amount of radiation that it absorbs. For example, if you were to shine a flashlight on a mirror, the light …
Dynamic Control Of Radiative Surface Properties With Origami-Inspired Design, Rydge B. Mulford, Matthew R. Jones, Brian D. Iverson
Dynamic Control Of Radiative Surface Properties With Origami-Inspired Design, Rydge B. Mulford, Matthew R. Jones, Brian D. Iverson
Faculty Publications
Thermal management systems for space equipment commonly use static solutions that do not adapt to environmental changes. Dynamic control of radiative surface properties is one way to respond to environmental changes and to increase the capabilities of spacecraft thermal management systems. This paper documents an investigation of the extent to which origami-inspired surfaces may be used to control the apparent absorptivity of a reflective material. Models relating the apparent absorptivity of a radiation shield to time-dependent surface temperatures are presented. Results show that the apparent absorptivity increases with increasing fold density and indicate that origami-inspired designs may be used to …
Measurement And Modeling Of Fire Behavior In Leaves And Sparse Shrubs, Dallan R. Prince
Measurement And Modeling Of Fire Behavior In Leaves And Sparse Shrubs, Dallan R. Prince
Theses and Dissertations
Wildland fuels and fire behavior have been the focus of numerous studies and models which provide operational support to firefighters. However, fuel and fire complexity in live shrubs has resulted in unexpected and sometimes aggressive fire behavior. The combustion of live fuels was studied and modeled, and the results were assimilated into a shrub-scale fire behavior model which assumes fire spread by flame-fuel overlap. Fire spread models have usually assumed that radiation heat transfer is responsible for driving fire spread, but that assumption is a topic of continuing debate, and appears to contradict some experimental observations. A convection-based shrub-scale fire …
Characterization And Optimization Of Thermal Protective Fabrics Designed To Protect Against Splash Hazards, Jeremy Osguthorpe
Characterization And Optimization Of Thermal Protective Fabrics Designed To Protect Against Splash Hazards, Jeremy Osguthorpe
Theses and Dissertations
Thermal textiles used in Personal Protective Equipment (PPE) are used to protect individuals from the hazards of thermal energy. An analytical model of the diffusion of thermal energy within the fabric was developed to simulate the transfer of thermal energy due to a hot liquid splash. Based on the model results, it was determined that that the use of an orthotropic material in which the thermal conductivities in the radial and axial directions are different can be used to decrease the amount of heat transferred through the fabric and thereby increase amount of protection in PPE. An orthotropic material particularly …
Thermal Transport To Sessile Water Droplets On Heated Superhydrophobic Surfaces Of Varying Cavity Fraction, Robb C. Hays
Thermal Transport To Sessile Water Droplets On Heated Superhydrophobic Surfaces Of Varying Cavity Fraction, Robb C. Hays
Theses and Dissertations
The hydrophobicity of a surface is defined as the degree to which it repels water molecules, and the internal contact angle that the droplet makes with the surface is a measure of the hydrophobicity. Contact angles less than 90° occur on hydrophilic surfaces, while contact angles greater than 90° occur on hydrophobic surfaces. If a surface's contact angle is greater than 120° the surface is commonly defined as superhydrophobic (SH). Superhydrophobicity is accomplished through a combination of microscale surface roughness and water repellant surface chemistry. The roughness creates cavities, or pockets, of vapor underneath the droplet which act to increase …
Measurement Of Thermal Diffusivities Using The Distributed Source, Finite Absorption Model, James B. Hall
Measurement Of Thermal Diffusivities Using The Distributed Source, Finite Absorption Model, James B. Hall
Theses and Dissertations
Thermal diffusivity in an important thermophysical property that quantifies the ratio of the rate at which heat is conducted through a material to the amount of energy stored in a material. The pulsed laser diffusion (PLD) method is a widely used technique for measuring thermal diffusivities of materials. This technique is based on the fact that the diffusivity of a sample may be inferred from measurement of the time-dependent temperature profile at a point on the surface of a sample that has been exposed to a pulse of radiant energy from a laser or flash lamp. An accepted standard approach …
Note: Thermal Analog To Atomic Force Microscopy Force-Displacement Measurements For Nanoscale Interfacial Contact Resistance, Brian D. Iverson, John E. Blendell, Suresh V. Garimella
Note: Thermal Analog To Atomic Force Microscopy Force-Displacement Measurements For Nanoscale Interfacial Contact Resistance, Brian D. Iverson, John E. Blendell, Suresh V. Garimella
Faculty Publications
Thermal diffusion measurements on polymethylmethacrylate-coated Si substrates using heated atomic force microscopy tips were performed to determine the contact resistance between an organic thin film and Si. The measurement methodology presented demonstrates how the thermal contrast signal obtained during a force-displacement ramp is used to quantify the resistance to heat transfer through an internal interface. The results also delineate the interrogation thickness beyond which thermal diffusion in the organic thin film is not affected appreciably by the underlying substrate.
Thermal Analog To Afm Force-Displacement Measurements For Nanoscale Interfacial Contact Resistance, Brian D. Iverson, John E. Blendell, Suresh V. Garimella
Thermal Analog To Afm Force-Displacement Measurements For Nanoscale Interfacial Contact Resistance, Brian D. Iverson, John E. Blendell, Suresh V. Garimella
Faculty Publications
Thermal diffusion measurements on PMMA-coated Si substrates using heated AFM tips were performed to determine the contact resistance between an organic thin film and Si. The measurement methodology presented demonstrates how the thermal contrast signal obtained during a force-displacement ramp is used to quantify the resistance to heat transfer through an internal interface. The results also delineate the interrogation thickness beyond which thermal diffusion in the organic thin film is not affected appreciably by the underlying substrate.
Radiation And Convection Heat Transfer In Wildland Fire Environments, David J. Frankman
Radiation And Convection Heat Transfer In Wildland Fire Environments, David J. Frankman
Theses and Dissertations
Wildland fire research has been extensive and on going since before 1950. The motivation behind this research is to prevent loss of property and lives. In spite of this research, the heat transfer of fuel ignition and flame spread is not well understood. This dissertation seeks to fill gaps in this understanding through modeling and also by experimentation. The effect of water vapor on the transmission of thermal radiation from the flame to the fuel was investigated. The Spectral Line Weighted-sum-of-gray-gases approach was adopted for treating the spectral nature of the radiation. The study reveals that water vapor has only …
Evolution Of Turbine Blade Deposits In An Accelerated Deposition Facility: Roughness And Thermal Analysis, James Edward Wammack
Evolution Of Turbine Blade Deposits In An Accelerated Deposition Facility: Roughness And Thermal Analysis, James Edward Wammack
Theses and Dissertations
During the operation of a gas turbine, ingested contaminants present in the air form deposits on the surfaces of the turbine blades. These deposits grow over time, resulting in an increasingly rough surface. This gradual increase in roughness results in several negative consequences, among which is an increase in the rate of heat transfer to the blade which shortens blade life. This thesis presents research in which deposits were evolved on three different turbine blade coupons and their evolution was studied. A trend in roughness change over time was discovered. Also, an attempt was made to find the effect of …
Approximate Thermal Modeling Of Radiofrequency Cardiac Ablation, Aaron Joseph Walter
Approximate Thermal Modeling Of Radiofrequency Cardiac Ablation, Aaron Joseph Walter
Theses and Dissertations
The ultimate objective of the research which led to this thesis is to increase the efficacy and safety of radiofrequency catheter ablation (RFCA) of cardiac tissue. The purpose of RFCA is to carefully heat selected locations in the heart. The resulting thermal injury creates lesions which prevent the generation or propagation of arrhythmias. The ability to predict the appropriate amount of energy required at any ablation site is essential to increasing the efficacy and safety of RFCA. The research documented in this thesis focuses on the development of an approximate thermal model of the time-dependent temperature profile within the myocardium …
Thermally Developing Electro-Osmotic Convection In Circular Microchannels, Spencer L. Broderick
Thermally Developing Electro-Osmotic Convection In Circular Microchannels, Spencer L. Broderick
Theses and Dissertations
Thermally developing, electro-osmotically generated flow has been analyzed for a circular microtube under imposed constant wall temperature (CWT) and constant wall heat flux (CHF) boundary conditions. Established by a voltage potential gradient along the length of the microtube, the hydrodynamics of such a flow dictate either a slug flow velocity profile (under conditions of large tube radius-to-Debye length ratio, a/lambda_d) or a family of electro-osmotic flow (EOF) velocity profiles that depend on a/lambda_d. The imposed voltage gradient results in Joule heating in the fluid with an associated volumetric source of energy. For this scenario coupled with a slug flow velocity …
The Development Of An Accelerated Testing Facility For The Study Of Deposits In Land-Based Gas Turbine Engines, Jared Wilfred Jensen
The Development Of An Accelerated Testing Facility For The Study Of Deposits In Land-Based Gas Turbine Engines, Jared Wilfred Jensen
Theses and Dissertations
Turbine engine efficiency modeling depends on many parameters related to fluid dynamics and heat transfer. Many of these parameters change dynamically once the engine enters service and begins to experience surface degradation. This thesis presents a validation of the design and operation of an accelerated testing facility for the study of foreign deposit layers typical to the operation of land-based gas turbines. It also reports on the use of this facility in an effort to characterize the change in thermal resistance on the surface of turbine blades as deposits accumulate. The facility was designed to produce turbine deposits in a …