Engineering Commons^™

Heat Transfer Enhancement By Three-Dimensional Surface Roughness Technique In Nuclear Fuel Rod Bundles, Kang Liu

Theses and Dissertations

DISS_abstract> This thesis investigate thermal characteristic of a single-phase nano-fluid in a single heater element loop tester and provides a comparison between heat transfer enhancement results achieved using water as a coolant and using nano-fluids with different volume percentage. The experimental investigation is performed on two simulated nuclear fuel rods with two different types of modified outer surfaces roughness. The fuel rod surfaces modified are termed as two-dimensional surface roughness (square transverse ribbed surface) and three-dimensional surface roughness (Diamond shaped blocks). The nano-fluid used are 0.5% and 2% ZnO-Deionized water based nano-fluid. The maximum heat transfer co-efficient enhancement achieved compared …

Numerical Modeling Of Infrared Thermography Techniques Via Ansys, Hayder Abdulnabi Thajeel

Masters Theses

"Several inspection techniques have been developed over years. Recently, infrared thermography (IRT) technology has become a widely accepted as a nondestructive inspection (NDI) technique for different fields and various applications as well. Infrared thermography stands as one of the most an attractive and a successful NDI technique that has ability to detect the object's surface/subsurface defects remotely based on observing and measuring the surface's emitted infrared heat radiation by using an infrared camera. The finite element modeling FEM ANSYS was successfully used for the modelling of several IRT techniques; such as Pulsed Thermography (PT) and Lock-in Thermography (LT) that can …

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 …

Applicability Of A Picosecond Laser For Micro-Polishing Of Metallic Surfaces, Abdullah Mohammad Khalid Hafiz

Electronic Thesis and Dissertation Repository

An increasing number of recent technological advancements is linked to the adoptions of ultra-short pulsed picosecond (ps) lasers in various material processing applications. The superior capability of this laser is associated with precise control of laser-material interaction resulted from extremely short interaction time. In this context, the present study explored the applicability of a ps laser in laser micro-polishing (LµP) of Inconel 718 (IN718) and AISI H13 tool steel. The melting regime ‒ a mandatory phase for LµP ‒ was determined experimentally by the variation of focal offset to attain desired laser fluence. The finite element formulation of heat transfer …

Computational Fluid Dynamics Validation Of Buoyant Turbulent Flow Heat Transfer, Jared M. Iverson

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Computational fluid dynamics (CFD) is commonly used to visualize and understand complicated fluid flow and heat transfer in many industries. It is imperative to validate the CFD computer models in order to avoid costly design choices where experimentation cannot be used to ratify the predictions of computer models. Assessments of CFD computer models in the literature conclude that significant errors occur in computer model predictions of fluid flow influenced by buoyancy forces.

The Experimental Fluid Dynamics Laboratory at Utah State University constructed a wind tunnel with which to perform experiments on buoyancy induced fluid flow. The experiments measured the heat …

Computational Analysis To Enhance Laminar Flow Convective Heat Transfer Rate In An Enclosure Using Aerosol Nanofluids, Andrew Hudson

Electronic Theses and Dissertations

The current research intends to provide a starting point to effectively model aerosol heat transfer in a narrow, enclosed body. This research can lead to future modeling of nano fluids including their heat transfer characteristics and erosion effects on the walls of an enclosure. The model was developed using ICEM CFD for the mesh and FLUENT for the fluid flow modeling. Six different aspect ratio enclosures were developed to study the effects of varying aspect ratio. The natural convection of air was developed first to establish the appropriateness of the models being used. A mesh check was performed using one …

Determination Of Heat Transfer In Under-Floor Plenums In Buildings With Under-Floor Air Distribution Systems, Yan Xue

Open Access Theses

Under-Floor Air Distribution (UFAD) systems have potential advantages of energy saving and indoor air quality improvement over conventional well-mixed systems. As a ventilation strategy for buildings, a UFAD system provides conditioned air to occupied rooms through diffusers in raised floors and the air is exhausted through return grilles at the ceiling level.

Many previous researches have focused on the energy saving and air quality improvement by UFAD systems because of their high supply air temperature and room air stratification. However, few of them paid attention to the effects of the heat transfer through floor slabs on the energy performance of …

Pressure And Heat Flux Effects On The Heat Transfer Characteristics Of Liquid Methane, Chance Paul Garcia

Open Access Theses & Dissertations

The heat transfer effects on liquid methane are investigated with the use of a carbo-thermal rig at the Center for Space Exploration Technology Research (cSETR) located at the University of Texas at El Paso (UTEP). The cSETR carbo-thermal rig design approach is presented along with the design of a methane condensing mobile unit (MCMU) to supply the laboratory and rig with liquid methane. The proposed research will generate useful insight in to heat transfer coefficient behavior, non-dimensional correlations, different flow conditions, varied inlet conditions, and varied heat flux for a subscale test article applicable to a regenerative cooled rocket engine …

Design, Manufacturing, And Assembly Of A Flexible Thermoelectric Device, Christopher Anthony Martinez

USF Tampa Graduate Theses and Dissertations

This thesis documents the design, manufacturing, and assembly of a flexible thermoelectric device. Such a device has immediate use in haptics, medical, and athletic applications. The governing theory behind the device is explained and a one dimensional heat transfer model is developed to estimate performance. This model and consideration for the manufacturing and assembly possibilities are the drivers behind the decisions made in design choices. Once the design was finalized, manufacturing methods for the various components were explored. The system was created by etching copper patterns on a copper/polyimide laminate and screen printing solder paste onto the circuits. Thermoelectric elements …

Boiling And Evaporation On Micro/Nanoengineered Surfaces, Xianming Dai

Theses and Dissertations

Two-phase transport is widely used in energy conversion and storage, energy efficiency and thermal management. Surface roughness and interfacial wettability are two major impact factors for two-phase transport. Micro/nanostructures play important roles in varying the surface roughness and improving interfacial wettability. In this doctoral study, five types of micro/nanoengineered surfaces were developed to systematically study the impacts of interfacial wettability and flow structures on nucleate boiling and capillary evaporation. These surfaces include: 1) superhydrophilic atomic layer deposition (ALD) coatings; 2) partially hydrophobic and partially hydrophilic composite interfaces; 3) micromembrane-enhanced hybrid wicks; 4) superhydrophilic micromembrane-enhnaced hybrid wicks, and 5) functionalized carbon …

Steady And Unsteady Thermo-Strucural Simulation Of Thermally Actuated Micro- And Nano-Structures, Elham Maghsoudi

LSU Doctoral Dissertations

This dissertation provides a thermo-structural simulation for nano-scale and micro-scale structures with pinned and fixed boundary conditions which are either thermally positioned, buckled, or actuated. The study begins with simulating a pinned-pinned beam in micro-scale and nano-scale. The steady state thermo-structural equation is solved numerically using an implicit Finite Difference method implemented in Matlab to obtain the thermal positioning response, which is the thermally steady state center displacement, by adding a constant, time-independent heat flux to the structure. The results show the steady state thermal displacement of the system is a function of the geometry, pressure, material properties, and constant …

Design And Simulation Of Passive Thermal Management System For Lithium-Ion Battery Packs On An Unmanned Ground Vehicle, Kevin Kenneth Parsons

Master's Theses

The transient thermal response of a 15-cell, 48 volt, lithium-ion battery pack for an unmanned ground vehicle was simulated with ANSYS Fluent. Heat generation rates and specific heat capacity of a single cell were experimentally measured and used as input to the thermal model. A heat generation load was applied to each battery and natural convection film boundary conditions were applied to the exterior of the enclosure. The buoyancy-driven natural convection inside the enclosure was modeled along with the radiation heat transfer between internal components. The maximum temperature of the batteries reached 65.6 °C after 630 seconds of usage …

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 …

Silicon Wafer Temperature Distribution, Daniel Gonzalez, Nathan Jones, Dylan Justice

Mechanical Engineering

Applied Materials is a global company that designs equipment for use in the semiconductor manufacturing industry. The scope of this project covers process chambers used for depositing thin chemical films onto silicon wafers. These processes must take place in particularly specific environments– including extremely low pressures and high temperatures. One challenge engineers face when designing these processes is carefully controlling the thermal behavior of silicon wafers. Typically, behavior is predicted using time consuming and computationally expensive CFD simulations. We have been asked to address this issue with a simpler, faster model which will allow engineers to reduce the total number …

An Investigation Of Mist/Air Film Cooling With Application To Gas Turbine Airfoils, Lei Zhao

University of New Orleans Theses and Dissertations

Film cooling is a cooling technique widely used in high-performance gas turbines

to protect turbine airfoils from being damaged by hot flue gases. Film injection holes are

placed in the body of the airfoil to allow coolant to pass from the internal cavity to the

external surface. The ejection of coolant gas results in a layer or “film” of coolant gas

flowing along the external surface of the airfoil.

In this study, a new cooling scheme, mist/air film cooling is proposed and

investigated through experiments. Small amount of tiny water droplets with an average

diameter about 7 μm (mist) is …

Flow Distribution And Heat Transfer Coefficients Inside Gas Holes Discharging, Amirhossein Eshtiaghi

LSU Master's Theses

Fluid flow and heat transfer coefficient associated with flow inside short holes (L/D=1) discharging orthogonally into a crossflow was investigated experimentally and numerically for (Re) ̅ ranging from 0.5×105 to 2×105, and blowing ratio ranging from 1.3 to 3.2. The basic configuration studied consists of a feed tube with five orthogonally located gas holes. Four different hole configurations were studied. The transient heat transfer study employs an IR-camera to determine the local heat transfer coefficient inside each hole. Velocity measurements and numerical flow simulation were used to better understand the measured heat transfer distribution inside the hole. The Nusselt number …

Multiobjective Design Optimization Of Gas Turbine Blade With Emphasis On Internal Cooling, Narasimha Nagaiah

Electronic Theses and Dissertations

In the design of mechanical components, numerical simulations and experimental methods are commonly used for design creation (or modification) and design optimization. However, a major challenge of using simulation and experimental methods is that they are timeconsuming and often cost-prohibitive for the designer. In addition, the simultaneous interactions between aerodynamic, thermodynamic and mechanical integrity objectives for a particular component or set of components are difficult to accurately characterize, even with the existing simulation tools and experimental methods. The current research and practice of using numerical simulations and experimental methods do little to address the simultaneous “satisficing” of multiple and often …

Flow Loop Simulator, John Abruzzini, Manuel Carrasco, Neil Sutherland, Elise Woolworth

Mechanical Engineering

PG&E’s Diablo Canyon Power Plant (DCPP) has requested an operational flow loop simulator to aid in operator/technician training. The flow loop simulator will provide hands-on training that the current plant training process cannot model. This project is a continuation from the 2009-2010 school year. Project scope and design requirements were gathered from the previous group’s design reports as well as meetings with PG&E. The goal of this year’s project team is to verify, enhance and implement the schematic diagram proposed by last year’s team.

The main focus of the flow loop simulator is to provide operators and technicians with …

Comparison Of Horizontal Ground Source (Geothermal) Heat Pump Layouts For Optimal Performance And Thermal Efficiency, Elizabeth M. Bocchino

Honors Theses

This study investigates the difference in thermal efficiencies of horizontal ground source heat pump layouts through computer simulation and experimental modeling. The main objective of this project was to determine if the shape of the layout affects the total heat exchange in a horizontal geothermal system. Geothermal energy is power extracted from the Earth and studies have been focused on increasing the efficiency of the heat transfer from the Earth to the system. Steady state and transient thermal analyses were conducted on two horizontal layout shapes, a U-loop and a coil, in ANSYS Fluent. This system was not full size, …

Modeling Of Non-Uniform Hydrodynamics And Catalytic Reaction In A Solids-Laden Riser, Rajeshkumar Patel

Dissertations

The riser reactors are widely used in a variety of industrial applications such as polymerization, coal combustion and petroleum refinery because of the strong mixing of gas and solids that yields high heat and mass transfer rates, and reaction rates. In a Fluid Catalytic Cracking (FCC) process, the performance of riser reactor is strongly dependent on the interaction between the fluid and catalysts, since the reaction takes place on the active surface of the catalysts. This is why, the local coupling between hydrodynamics and reaction kinetics is critical to the development of riser reaction models. The local gas-solids flow structure …

Fabrication And Testing Of A Nonstandard Thin-Film Heat Flux Sensor For Power System Applications, Scott D. Wilson

ETD Archive

Stirling convertors are being operated by NASA Glenn Research Center for many years to demonstrate a Radioisotope Power System (RPS) capable of providing reliable power for potential multi-year space missions. Techniques used to monitor Stirling convertors for change in performance include measurements of temperature, pressure, energy addition, and power output. It is difficult to measure energy addition to Stirling convertors due to the complex geometries of the hot components, temperature limits of sensor materials, and invasive integration of sensors. A thin-film heat flux sensor was used to directly measure heat energy addition to a Stirling convertor. The one micron thick, …

Development Of A Heat Transfer Test Rig For Finding Heat Transfer Characteristics Of Liquid Methane, Sergio Flores

Open Access Theses & Dissertations

Most large scale rocket engines use a regeneratively cooled system to cool the rocket engine using either the rocket fuel or oxidizer. The use of liquid methane as a rocket fuel is an emerging technology proving to have several advantages over current rocket fuels. However, liquid methane is lacking the extensive research as a rocket fuel compared to highly used rocket fuels like liquid hydrogen. A heat transfer test rig was built with the goal to characterize the heat transfer characteristics of liquid methane as it passes through a heated channel. The development of the test rig underwent considerations designed …

Pool Boiling Enhancement Via Micro Ratchets, Lance Austin Brumfield

LSU Master's Theses

Nucleate boiling is an attractive method for achieving high heat flux at low superheat temperatures. It is frequently used for industrial applications such as heat exchangers and is being considered to cool advanced central processing units (CPU) which produce heat fluxes on the order of 1 MW/m2 and are becoming increasing less efficient to cool via forced conduction of air. The issues with implementing nucleate boiling as a cooling mechanism lies in the difficulty of quantifying the complex and numerous mechanisms which control the process. A comprehensive nucleate boiling model has yet to be formulated and will required in order …

Flow Loop Simulator, Tyler Ista, Kevin Rehm, Matt Starbuck

Mechanical Engineering

PG&E’s Diablo Canyon Power Plant has requested a full-sized flow process system for training of technicians by providing them a hands-on experience in a controlled environment. The basic design requirements were established to determine the scope of the project. An initial system layout was selected from a variety of concepts after similar system schematics, components, and processes had been researched. The resulting schematic was flexible to suit several needs of the control aspect while remaining simple.

Design efforts resulted in a system capable of many configurations; allowing for implementation of three training experiments. These experiments involve control of tank level …

Experimental Investigation Of Flow And Heat Transfer Characteristics Of R -134a In Microchannels, Abdullahel Bari

Doctoral Dissertations

The purpose of this study was to investigate the flow and heat transfer characteristics of liquid refrigerant R-134a in rectangular microchannels. The research concentrated mostly upon single-phase experiments with limited investigation of boiling phenomenon in microchannels. Tests were performed using rectangular microchannels with hydraulic diameters ranging from 112 μm to 210 μm and aspect ratios varying approximately from 1.0 to 1.5. The Reynolds number in the experiments ranged from 1,200 to 13,000 although most data were collected in the transition and turbulent flow regimes.

The experimental data for friction factor measurement had a similar trend as predicted by macroscale theory …

Designing Of Energy Efficient Indoor Environments Using A Localized Radial Basis Function Meshless Method, Victor Huayamave

Electronic Theses and Dissertations

Around the world, the energy over consumption issue has been one of the key socio-economic and political challenges, which has drastically worsened over the last few years. Over the years engineers and environmentalists have proposed several approaches to improve energy efficiency. One is to reduce energy demand by improving consumption habits and a second approach is to introduce the use of a "greener" concept by using biomaterials in a diverse and more efficient manner in engineering construction to create energy efficient environments. This work will investigate the effects of using "green" stabilized earth materials to provide and enhance thermal regulation …

High Heat Flux Spray Cooling With Ammonia On Enhanced Surfaces, Huseyin Bostanci

Electronic Theses and Dissertations

Many critical applications today, in electronics, optics and aerospace fields, among others, demand advanced thermal management solutions for the acquisition of high heat loads they generate in order to operate reliably and efficiently. Current competing technologies for this challenging task include several single and two phase cooling options. When these cooling schemes are compared based on the high heat flux removal (100-1000 W/cm2) and isothermal operation (within several oC across the cooled device) aspects, as well as system mass, volume and power consumption, spray cooling appears to be the best choice. The current study focused on high heat flux spray …

A Model Integrated Meshless Solver (Mims) For Fluid Flow And Heat Transfer, Salvadore Gerace

Electronic Theses and Dissertations

Numerical methods for solving partial differential equations are commonplace in the engineering community and their popularity can be attributed to the rapid performance improvement of modern workstations and desktop computers. The ubiquity of computer technology has allowed all areas of engineering to have access to detailed thermal, stress, and fluid flow analysis packages capable of performing complex studies of current and future designs. The rapid pace of computer development, however, has begun to outstrip efforts to reduce analysis overhead. As such, most commercially available software packages are now limited by the human effort required to prepare, develop, and initialize the …

The Next Generation Router System Cooling Design, Garrett A. Glover

Master's Theses

Advancements in the networking and routing industry have created higher power electronic systems which dissipate large amounts of heat while cooling technology for these electronic systems has remained relatively unchanged. This report illustrates the development and testing of a hybrid liquid-air cooling system prototype implemented on Cisco’s 7609s router. Water was the working fluid through cold plates removing heat from line card components. The water was cooled by a compact liquid-air heat exchanger and circulated by two pumps. The testing results show that junction temperatures were maintained well below the 105°C limit for ambient conditions around 30°C at sea level. …

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 …