Mechanical Engineering Commons^™

Transient Thermal Performance Enhancement Of Phase Change Materials Through Novel Pin Arrangements Under Varied Gravity Conditions, Junaid Khan

Masters Theses

This thesis presents a comprehensive examination of encapsulation techniques and performance enhancement strategies for Phase Change Materials (PCMs) in the thermal management of spacecraft avionics. This research contributes to optimizing PCM applications in spacecraft through historical analysis, transient thermal performance enhancement, and computational studies.

The first chapter explains the significance of PCMs in passive thermal management since the beginning of space-age technology, it underlines the low thermal conductivity of PCMs and the necessity of incorporating materials with high thermal conductivity, such as metal foams, to improve heat transfer. It also discusses various advancements in PCM research for spacecraft thermal management …

Enabling Premixed Hydrogen-Air Combustion For Aeroengines Via Laboratory Experiment Modeling, Christopher James Caulfield

Masters Theses

All combustion systems from large scale power plants to the engines of cars to gas turbines in aircraft are looking for new fuel sources. Recently, clean energy for aviation has come into the foreground as an important issue due to the environment impacts of current combustion methods and fuels used. The aircraft industry is looking towards hydrogen as a new, powerful, and clean fuel of the future. However there are several engineering and scientific challenges to overcome before hydrogen can be deployed into the industry. These issues
range from storing the hydrogen in a viable cryogenic form for an aircraft …

Design, Fabrication, And Validation Of A Three-Zone Cell For Absorption Spectroscopy, Derek W. Burkhart

Masters Theses

Spectroscopic databases such as HITRAN and HITEMP are required to characterize the spectral parameters of chemical species to ensure accurate calculations of gas concentrations and temperatures from laser absorption spectroscopy. These databases are populated by performing spectroscopic experiments at controlled conditions. Databases lack spectral parameters for combustion species such as CO, CO2, and H2O at temperatures combustion temperatures in the mid-IR wavelength range due to difficulties in creating an experimental absorption cell capable of surviving combustion temperatures. A high temperature absorption cell was previously used at the University of Tennessee Space Institute (UTSI) for high temperature spectroscopic experiments with combustion …

Effects Of Pillar And Sealing Design On Thermal And Mechanical Performance Of Vacuum Insulated Glazing, Wenyuan Zhu

Masters Theses

Vacuum insulated glazing with a low-emittance coating has a great market potential as an effective transparent insulator. The thermal insulating performance of VIG is determined by its design, including material selection and configuration of different components. Thermal conductance of the vacuum gap, as a transport bottleneck, is one of the primary factors controlling the thermal transport across VIG. In particular, since support pillars and sealings provide the main thermal transport channels across the vacuum gap, increasing the pillar and sealing thermal resistance is a key strategy for effective thermal insulation, while maintaining the vacuum space and mechanical strength of VIG. …

Experimental Investigation Of Spray Cooling/Heating Of A Near-Isothermal Hydro-Pneumatic Energy Storage System, Saiid Kassaee

Masters Theses

Proposing experimental investigation of spray cooling/heating of a near-isothermal, scalable, efficient, high density, hydro-pneumatic integrated energy storage system; capable of spray cooling/heating during gas compression/expansion and capable of excess heat integration. The invented Ground-Level Integrated Diverse Energy Storage (GLIDES) is an energy storage technology capable of storing energy in high-pressure vessel using hydro-pneumatic concept. Indicated roundtrip efficiencies of 98% can be reached using the proposed technology marking an isothermal compression/expansion energy storage.

Survivability Investigation Of Cylindrical Shaped Water Cooled Probe In High Heat Flux Conditions, Joshua Osborne

Masters Theses

Diagnostics and data collection downstream of turbine engine augmentors and scramjet combustors provide critical information for turbine engine and scramjet engine developers. One important diagnostic tool is the use of imaging measurement instruments, which are primarily used by the aeropropulsion ground testing community to assess flame holder stability and uniformity in turbine engines. The survivability limitations of these imaging probes are important to understand for use in applications behind ramjet or scramjet engines, where mass flows and exhaust temperatures exceed typical engine augmentor exhaust streams. At a minimum, imaging data acquired behind ramjet and scramjet engines would be used to …

Nanoscale Investigations Of Thermal And Momentum Transport In Graphene – Water Systems, Drew Champion Marable

Masters Theses

Demand for miniaturized electronic devices has given rise to new challenges in thermal management. Integration with graphene, a two-dimensional (2D) material with excellent thermal properties, allows for further reduced sizes and combats thermal management issues within novel devices. Moreover, due to its wide availability and adequate thermal properties, liquid water is commonly used within traditional thermal systems to enhance cooling performance; as such, water is expected to yield similar performance in smaller-scale applications. However, at reduced sizes descending to the nanoscale realm, system behaviors deviate from traditional macroscale-based theory as interfacial effects become amplified. Employing insight provided by molecular dynamics …

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 …

Laser Diagnostics Of C2h4 And Ch4 From N-Butane Pyrolysis, Liu Su

Masters Theses

Combustion of fossil fuels remains the dominant source of energy which enables us sustain thrive in this planet. Meanwhile, the negative effects of burning fossil fuels, however, are devastating our climate and environment. Eliminating those negative effects while attaining energy supply from fossil fuels becomes urgent and prominent. It is, nevertheless, impossible without a thorough understanding of the combustion process.

Experimental approach remains one of the dominating approaches to study combustion despite the growing interest in numerical approach. The development of workstations and massive supercomputers is providing the computation ability that one has never imaged. Nevertheless, it still appears difficult …

Improved Modeling Of Atmospheric Entry For Meteors With Nose Radii Between 5cm And 10m, Jakob Dale Brisby

Masters Theses

Atmospheric entry studies typically look closely at the peak heating rate that a body encounters during its trajectory. This is an extremely important phenomenon to study because it allows engineers to determine if a trajectory is possible with given materials and craft design specifications. It also allows designers to choose what type of method will be used for mitigating the enormous heat fluxes during entry. In general, it is accepted that during the super-sonic flight regime the body will continue to be heated and an ablative heat shield often is used to deal with these heating processes. The theory outlined …

Extending The Lean Limit Of Methane-Air Mixtures By Oxygen, Nitrogen And Carbon Dioxide Injection In The Gap Of The Spark Plug’S Electrodes, Artem Alexandrov Temerev

Masters Theses

An experimental investigation is carried out to investigate the feasibility of extending the lean limit for methane–air mixtures by injecting oxygen and other gases such as nitrogen and carbon dioxide in the area between spark plug electrodes. Additionally, the effect of oxygen injection on exhaust gas recirculation (EGR) is investigated. The pressure in the chamber and the equivalence ratio of the mixture are varied from 0.35 MPa to 1.03 MPa and 0.46 to 1.0, respectively. Delco 12620540 spark plug is used as the ignition source and the gas injection into spark plug gap is accomplished through a 0.159-cm OD stainless …

Design And Fabrication Of A Low-Cost Turbine Engine Component Testbed (Tect), Joshua A. Hartman

Masters Theses

With gas turbine engine testing becoming very expensive because of the increasing complexity involved with the engine, engine subsystems, and test support systems, a low-cost Turbine Engine Component Testbed (TECT) is proposed. This engine build is given the designation J1-H-02. In the present study, a small augmented gas turbine engine (GTE) is constructed. The TECT engine is built with modularity as a key design consideration to allow for flame-tube patterns and augmentor sections to be changed quickly for combustion experiments that have gained impetus due to combustion anomalies/instabilities inherent with future military engine augmentors. This testbed allows for an effective …

Thermal Response Characterization And Low Fluid Velocity Measurements Using Specialized In-Situ Thermocouples Via The Loop Current Step Response Method, Alexander Hashem Hashemian

Masters Theses

In this study, a specialized balanced-leads thermocouple was developed to perform in-situ thermal response characterization via the LCSR test method. Thermal response characterization of installed thermocouples is essential in order to obtain accurate positional temperature data in rapid transient applications. An analytical model is presented that fully describes the thermocouple system based on a first-principles approach to the heat transfer physics of the sensor. In conjunction with the LCSR test, the full model presented yields quantifiable characterization parameters useful for determining accurate positional temperature data. It is necessary to employ a balanced-leads thermocouple for this experimental procedure in order to …

Neutron Imaging Of Lithium (Li) Coolants Inside High Temperature Niobium (Nb) Heat Pipes, Brad Harrison Hight

Masters Theses

Lithium (Li) behavior inside a high temperature Nb-Li leading edge heat pipe was successfully imaged under induction heating operation via neutron imaging. Startup and cool-down operations gave visual confirmation of bulk Li movement using both gravity assisted and inverted operating orientations. The pipe was imaged during an operation cycle from ambient conditions, heated to a steady state temperature of 908.8 ⁰C, and allowed to cool below 200^°C. The experiment was performed at the National Institute of Standards and Technology (NIST) in Gaithersburg, Maryland, and at the Oak Ridge National Laboratory (ORNL) in Oak Ridge, Tennessee.

Tomographic images …

Formulation And Experimental Verification Of Alternate Calibration Techniques Of The Temperature Dependent Response Of Phosphor Fluorescence, Kelsey Michele Winstead

Masters Theses

The overall goal of this work is to provide an alternative approach to the thermographic phosphor (TP) time constant calibration method for temperature recovery. In this work two techniques are proposed that retain the pulsed source input used in the standard TP time constant calibration approach but reinterpret the phosphor response taken a fixed distance such that the single-exponential decay assumption is removed. The methods do not require knowledge of key parameters prior to data processing, nor do they involve complicated numerical schemes that attempt to fit data in the low signal-to-noise region of the phosphor response. The approaches do …

A Novel Approach To Multiphysics Modeling Of Heat And Mass Transfer In Porous Media, Seth Allen Pemberton

Masters Theses

This thesis aims to investigate conjugate heat and mass transfer in porous media with an emphasis on textiles. Both hygroscopic materials, those that absorb water vapor, and non-hygroscopic materials are examined. A model was developed that utilizes COMSOL’s equation-based partial differential equation (PDE) interface which allows the user to input any equation(s) to be solved. By the use of experimental and numerical data each part of the model, i.e. flow field, gas diffusion, convection and vapor absorption, is verified. The accuracy of the equation-based unsteady flow field is verified by modeling the flow over a circular cylinder and extracting the …

Modeling And Validation Of Heat Transfer Present In A Solar Thermal Collector, Eric Ezekiel Stannard

Masters Theses

A solar absorber panel for a solar water heating system located at the College of Architecture’s New Norris House in Norris, TN was modeled and validated against field data in this work. The purpose of this modeling was to create the foundations of a tool that can be used in collector design and building energy simulations. This tool would take into account the radiometric properties of the collector materials, which are essential for an accurate model. Solar water heaters convert the shortwave energy of the Sun into usable heat for residential and industrial applications and have the potential to greatly …

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’ …

Direct Measurement Of Through-Plane Thermal Conductivity Of Partially Saturated Fuel Cell Diffusion Media, Guoqing Xu

Masters Theses

Polymer electrolyte fuel cells (PEFCs) are predicted by many as the most feasible alternative to heat engines and for battery replacement in automotive, portable, and stationary power applications. Fuel cell performance and durability are inseparably related to the presence of liquid water throughout the fuel cell system. To better understand the mechanical and thermal characterization of diffusion media (DM) is essential to PEFC DM design, optimization and production to improve water and thermal managements. Diffusion media are one of the important components in PEFCs in terms of the reactant permeability, the product permeability, the electronic conductivity, the heat conductivity, and …

Water Transport In Polymer Electrolyte Fuel Cells: An Exploration Of Net Water Drag In Real Time, Susan Katherine Reid

Masters Theses

Polymer electrolyte fuel cells (PEFCs) are a promising alternative energy source. One challenge preventing widespread use of this technology is water management. A balance must be reached between providing sufficient water for membrane ionic conductivity while maintaining low enough water content to mitigate the reduction of available reaction sites in the cathode catalyst layer due to liquid water build up. Much exploration of this area of fuel cell research has been conducted, but the details of water transport in an operating fuel cell are not yet fully understood. The motivation of this work was to elucidate mass transport phenomena occurring …

A Thermal Feasibility Study And Design Of An Air-Cooled Rectangular Wide Band Gap Inverter, Jacob Christopher Faulkner

Masters Theses

All power electronics consist of solid state devices that generate heat. Managing the temperature of these devices is critical to their performance and reliability. Traditional methods involving liquid-cooling systems are expensive and require additional equipment for operation. Air-cooling systems are less expensive but are typically less effective at cooling the electronic devices. The cooling system that is used depends on the specific application.

Until recently, silicon based devices have been used for the solid-state devices in power electronics. Newly developed silicon-carbide based wide band gap devices operate at maximum temperatures higher than traditional silicon devices. Due to the permissible increase …

Cross-Flow, Staggered-Tube Heat Exchanger Analysis For High Enthalpy Flows, Gary L. Hammock

Masters Theses

Cross flow heat exchangers are a fairly common apparatus employed throughout many industrial processes. For these types of systems, correlations have been extensively developed. However, there have been no correlations done for very high enthalpy flows as produced by Arnold Engineering Development Center’s (AEDC) H2 facility. The H2 facility uses a direct current electric arc to heat air which is then expanded through a converging-diverging nozzle to impart a supersonic velocity to the air. This high enthalpy, high temperature air must be cooled downstream by the use of a cross flow heat exchanger.

It is of interest to evaluate the …

Modeling And Analysis Of Turbojet Compressor Inlet Temperature Measurement System Performance, Brian A Binkley

Masters Theses

Accurate measurement of turbine engine compressor inlet total temperature is paramount for controlling engine speed and pressure ratio. Various methods exist for measuring compressor inlet total temperature on turbojet engines with hydromechanical control. One method involves the use of an ejector-diffuser system (eductor) to pull air from the engine inlet in order to measure the incoming total temperature. Analysis of historical test data has revealed that the inlet temperature measurement can be biased at certain flight conditions causing engine mis-scheduling and off-nominal engine operation. This bias is characterized primarily by adverse heat transfer effects and secondly by poor flow quality …

Thermal Feasibility And Performance Characteristics Of An Air-Cooled Axial Flow Cylindrical Power Inverter By Finite Element Analysis, Jonathan Atef Tawfik

Masters Theses

The purpose of the present study is to determine the thermal feasibility of an air-cooled power inverter. The inverter circuitry layout is designed in tandem with the thermal management of the devices. The cylindrical configuration of the air-cooled inverter concept accommodates a collinear axial air blower and a cylindrical capacitor with inverter cards oriented radially between them. Cooling air flows from the axial fan around the inverter cards and through the center hole of the cylindrical capacitor. The present study is a continuation of the thermal feasibility study conducted in fiscal year 2009 for the Oak Ridge National Laboratory to …

Determination Of Thermal Properties Using Embedded Thermocouples, Nicholas Anthony Lister

Masters Theses

The Purpose of this thesis is to experimentally demonstrate an inversion analysis technique, developed by Dr. Jay Frankel (UTK), that utilizes transient temperature data from probes embedded at known locations in a material. This allows one to determine thermal properties (thermal diffusivity and thermal conductivity) of the material, surface temperature, and the surface heat flux as they change with time. Dr. Frankel’s inversion method can be used to determine surface temperature and heat flux of a one-dimensional semi-infinite slab based on the transient data from one or two embedded probes, if the thermal conductivity and thermal diffusivity of the material …