Aerodynamics and Fluid Mechanics Commons^™

Thermal Radiation Effects On Particles From Plasma Arc Radiation, Reece Davis, Joseph Mcgee

Williams Honors College, Honors Research Projects

Understanding the radiation heating and transport of both microparticles and nanoparticles is a phenomenon that is critical for both space and Earth sciences. In space, these particles are heated by plasma arcs within ionized space clouds or solar flares and can be present the path of deep space missions and orbital satellites. While on Earth, processes such as forest fires, nuclear fusion, and microchip manufacturing include the plasma arc heating of particles. These particles lay within the Mie Scattering Regime and Rayleigh Scattering Regime and emit radiation differently based on their diameter. New mathematical and computational modeling has been conducted …

Experimental Investigation Of Heat Transfer To Tightly Packed Cylinder Arrays, Cameron M. Sexsmith

Doctoral Dissertations and Master's Theses

With the increased emphasis on the development of hybrid electric aircraft and other electric driven vehicles, the thermal demand on batteries is increasing. Unique to the aviation sector is the combined need of high battery thermal loads and a light-weight thermal management system. A proposed configuration is an array of batteries directly cooled with a dielectric coolant. The knowledge of heat transfer characteristics of battery cooling is becoming an ever pressing issue due to the need to optimize volume and mass in a safe manner. Tighter spacings between batteries provide higher pack densities, however, at the cost of increased cooling …

Heat Transfer In Tightly Packed Cylinder Arrays, Martin Kovachev

Doctoral Dissertations and Master's Theses

Cylindrical arrays with a cross flow are commonly used for heat transfer augmentation within an internal channel. In most applications, the cylinders have a spacing of over 2 diameters (2D) between their center points in both the lateral and downstream directions. One option for battery thermal management in hybrid/electric aviation is to use cylindrical batteries packed in arrays with an applied cross flow. In the context of aviation, it is important to maximize space and weight savings. Tightly packing these cylinder arrays with a spacing of under 2D in both directions would save on both of these yet have not …

Comprehensive Review Of Heat Transfer Correlations Of Supercritical Co2 In Straight Tubes Near The Critical Point: A Historical Perspective, Nicholas C. Lopes, Yang Chao, Vinusha Dasarla, Neil P. Sullivan, Mark Ricklick, Sandra Boetcher

Publications

An exhaustive review was undertaken to assemble all available correlations for supercritical CO2 in straight, round tubes of any orientation with special attention paid to how the wildly varying fluid properties near the critical point are handled. The assemblage of correlations, and subsequent discussion, is presented from a historical perspective, starting from pioneering work on the topic in the 1950s to the modern day. Despite the growing sophistication of sCO2 heat transfer correlations, modern correlations are still only generally applicable over a relatively small range of operating conditions, and there has not been a substantial increase in predictive capabilities. Recently, …

Editorial For The Special Issue On Micromachines For Non-Newtonian Microfluidics, Lanju Mei, Shizhi Qian

Mechanical & Aerospace Engineering Faculty Publications

In lieu of an abstract, this is an excerpt from the first page.

Microfluidics has seen a remarkable growth over the past few decades, with its extensive applications in engineering, medicine, biology, chemistry, etc [...]

Experimental Study Of Wall Bounded Harbor Seal Whisker Inspired Pin Geometries, Anish Prasad, Mark Ricklick

Publications

Conventional cylindrical/elliptical pins are one of the most widely used geometries in convection cooling systems and are used in the internal cooling of gas turbine blades and other applications, as they promote better heat transfer at the expense of large pressure losses and unsteadiness in the flow. The need to reduce pressure drop and maintain the heat transfer rates are a pressing requirement for a variety of industries to improve their cooling efficiency. One such prominent field of research is conducted in optimizing the design of pin geometries. In this study, a harbor seal whisker inspired geometry is being studied …

Computational Sodium Heat Pipe Simulation In Three Dimensions For Transient Nuclear Reactor Analysis With Variable Surface Heat Flux, Valerie Jean Lawdensky

UNLV Theses, Dissertations, Professional Papers, and Capstones

Heat pipes are used to transfer heat through phase change in a liquid/vapor contained in a metal tube. They are passive devices that require no pumps to circulate the fluid and can transfer heat far more efficiently than a solid copper rod of the same diameter. They are commonly used in laptop computers where copper heat pipes filled with water take heat away from the CPU and transfer the heat to air through a heat exchanger. Heat pipes were also used in the Kilopower nuclear reactor where higher temperatures required sodium as the working fluid with stainless steel tubes. Computer …

On The Local Heat Transfer Behavior Of Supercritical Carbon Dioxide, Neil Sullivan

Doctoral Dissertations and Master's Theses

A detailed study of the local heat transfer behavior of supercritical carbon dioxide (sCO2) is performed. Flows relevant to heat transfer devices, such as sCO2 heaters, recuperators, and internally cooled turbine blades are studied, with particular attention paid to data reduction methodology, and the use of appropriate reference quantities, nondimensionalizations, and correlations. Additionally, a semi-intrusive temperature measurement technique capable of obtaining highly spatially resolved temperature distributions is adapted for use in the challenging conditions of supercritical (SC) flow. SC fluids have proven difficult to study both experimentally and numerically due to dramatically changing thermodynamic and transport properties near the critical …

Computational Investigation Of Perforated Plate Film Cooling Utilizing Conjugate Heat Transfer, Jonathan Sippel

Doctoral Dissertations and Master's Theses

The accuracy of modern state-of-practice computational fluid dynamics approaches in predicting the cooling effectiveness of a perforated plate film-cooling arrangement is evaluated in ANSYS Fluent. A numerical investigation is performed using the Reynolds Averaged Navier Stokes equations and compared to NASA Glenn’s available Turbulent Heat Flux 4 experimental measurements collected as a part of the Transformational Tools and Technologies Project. A multiphysics approach to model heat conduction through the solid geometry is shown to offer significant improvements in wall temperature and film effectiveness prediction accuracy over the standard adiabatic wall approach. Additionally, localized gradient-based grid adaption is analyzed using the …

Analysis Of Local Convection Heat Transfer Rates Of Supercritical Carbon Dioxide In Tubes, Yang Chao

Doctoral Dissertations and Master's Theses

Numerical investigation on thermodynamic characteristics of pure supercritical carbon dioxide (𝑆𝐶𝑂2) and mixtures of Helium and 𝑆𝐶𝑂2 in horizontal straight tubes with diameter of 6mm under cooling and heating conditions is carried out by using SST 𝑘 − 𝜔 turbulence model. The computations are conducted at operating pressure of 8MPa with various operating conditions. Simulations are conducted by using the latest poly-hexcore mesh method in ANSYS FLUENT 19.2 and tetrahedral mesh method in CFX 19.2, results and solving time are compared. The effect of heat flux, mass flux, inlet temperature and buoyancy on heat transfer performance are studied, pressure drop …

Numerical Simulation Of Heat Transfer And Chemistry In The Wake Behind A Hypersonic Slender Body At Angle Of Attack, Matthew J. Satchell, Jeffrey M. Layng, Robert B. Greendyke

Faculty Publications

The effect of thermal and chemical boundary conditions on the structure and chemical composition of the wake behind a 3D Mach 7 sphere-cone at an angle of attack of 5 degrees and an altitude of roughly 30,000 m is explored. A special emphasis is placed on determining the number density of chemical species which might lead to detection via the electromagnetic spectrum. The use of non-ablating cold-wall, adiabatic, and radiative equilibrium wall boundary conditions are used to simulate extremes in potential thermal protection system designs. Non-ablating, as well as an ablating boundary condition using the “steady-state ablation” assumption to compute …

Extended Surface Heat Transfer Coefficients Via Endwall Temperature Measurements, Yogesh Pai

Doctoral Dissertations and Master's Theses

Short pins are used for internal cooling of the trailing edge in a gas turbine blade. A novel method is described in this thesis which helps in simplifying the experimental process used to obtain average heat transfer data on the pin surface, at the expense of additional post processing complexity. The method is based on a unique, analytical solution of the longitudinal conduction equation with internal heat generation, allowing computation of heat transfer rates via pin base temperature measurements via Temperature Sensitive Paint, or similar non-intrusive methods. Verification of this method is done with comparisons to the solution of infinite …

Heat Transfer Analysis Of An Oblique Jet Impingement Cooling On Cmc Rough Surface, Karthik Krishna

Doctoral Dissertations and Master's Theses

A Ceramic Matrix Composite is high strength and high temperature capability composite, utilized in components like heat shield of space vehicles, flame holders and disc brakes. To be used in both static and dynamic components of a future gas turbine engine and even with high temperature capabilities of these CMC components, convection cooling will still likely be required. The surface of the CMC varies significantly from traditional super-alloy used in a modern engine, with large level of roughness and significant three-dimensional waviness. These complex features will impact the behavior of the near wall flows, and affect the heat transfer rates …

Comparison Of Models For Mixture Transport Properties For Numerical Simulations Of Ablative Heat-Shields, Hicham Alkandry, Iain D. Boyd, Alexandre Martin

Mechanical Engineering Faculty Publications

The goal of this study is to evaluate the effects of different models for calculating the mixture transport properties on flowfield predictions of ablative heat-shields. The Stardust sample return capsule at four different trajectory conditions is used as a test case for this study. In the first part of the study, the results predicted using Wilke's mixing rule with species viscosities calculated using Blottner's curve fits and species thermal conductivities determined using Eucken's relation are compared to the results obtained using Gupta's mixing rule with collision cross-section (CCS) data. The Wilke/Blottner/Eucken model overpredicts the heat transfer to the surface relative …

Modeling Of Heat Transfer Attenuation By Ablative Gases During The Stardust Re-Entry, Alexandre Martin, Iain D. Boyd

Mechanical Engineering Faculty Publications

The great majority of modern space vehicles designed for planetary exploration use ablative materials to protect the payload against the high heating environment experienced during re-entry. In order to properly model and predict the aerothermal environment of the vehicle, it is imperative to account for the gases produced by ablation processes. In the case of charring ablators, where an inner resin is pyrolyzed at a relatively low temperature, the composition of the gas expelled into the boundary layer is complex and may lead to thermal chemical reactions that cannot be captured with simple flow chemistry models. In order to obtain …

Validation Of Conjugate Heat-Transfer Capability For Water- Cooled High-Speed Flows, Bruno R. Fletcher

Master's Theses - Daytona Beach

A FORTRAN conduction/convection heat transfer module named FOGO (meaning fire in Portuguese) has been developed to perform the conjugate heat transfer analyses with existing flow solvers. In this work, FOGO is coupled with TBD and WIND-US flow solvers. WIND-US is a well validated flow solver developed by NASA, AEDC, and Boeing. TBD is a new flow solver developed at ERAU. TBD is verified for laminar stagnation point heat transfer prediction and turbulent flowfield protection. The FOGO module is verified against an exact solution for transient one-dimensional heat flow in a semi-infinite solid

The coupled TBD-FOGO and WIND-FOGO conjugate heat-transfer solvers …

Effect Of High Free Stream Turbulence On Film Cooling Using Double Row Of 30° Slant-Hole Injectors, Lilith I. Sorensen

Theses and Dissertations

In this study free stream turbulence levels from 7.3% to 17.8% are applied to film cooling over a flat plate with two rows of 30° slant holes using a wall jet as the main stream air supply and source of turbulence. Blowing ratios are varied from 0.25 to 2.0 and free stream velocities at injection range from 10 m/s to 85 m/s. A constant density ratio of 1.07 is kept throughout the experiment. Results show that for different magnitudes of blowing ratio free stream turbulence has a different influence on effectiveness. At the forward stations, where blow off was present …