Novel Methods for Studying Human Heat Transfer Using a Thermal Manikin: Extreme Heat Enabled Thermo-Physiological Simulation and Radiation Filtering

Description
Extreme heat exposure is a rising threat to human health due to rapid urbanization and climate change. To combat this, the scientific community has taken interest in the modeling of human health outcomes to these extreme conditions. Traditional methods for

Extreme heat exposure is a rising threat to human health due to rapid urbanization and climate change. To combat this, the scientific community has taken interest in the modeling of human health outcomes to these extreme conditions. Traditional methods for assessing heat exposure are often limited in their ability to simulate real-world conditions, particularly in hot outdoor environments. This research aims to address these gaps by advancing thermal manikin testing methodologies to better model human health outcomes in extreme heat scenarios.This work explores novel testing methods for evaluating thermal comfort and heat exposure using a thermal manikin, with a focus on two experimental approaches: The primary objective is to develop a new coupling method between the manikin and a thermophysiological model to enable its use in extreme heat environments. Additionally, a method of isolating the effects of both short and long wave radiation incident on the human body by manipulating the spectral properties of a thermal manikin is tested. The results demonstrate that the new model coupling method was effective and can replicate human subject response to extreme heat. However, there were certain discrepancies when compared to human subject data that need to be investigated. Of the two radiation isolation methods attempted, one failed to be viable while the other proved to be effective in quantifying short and longwave effects on the body.

Details

Contributors
Date Created
2024
Embargo Release Date
Resource Type
Language
  • eng
Note
  • Partial requirement for: M.S., Arizona State University, 2024
  • Field of study: Engineering

Additional Information

English
Extent
  • 73 pages
Open Access
Peer-reviewed

Growth and Characterization of Room Temperature Topological Magnetic Materials

Description
Magnetic textures, like skyrmions, merons, and domain walls are predicted to be future for the next-generation data-storage and information-transfer technologies due to their ultrafast spin-switching capabilities. However, most of these textures exist at low temperatures which is an issue for

Magnetic textures, like skyrmions, merons, and domain walls are predicted to be future for the next-generation data-storage and information-transfer technologies due to their ultrafast spin-switching capabilities. However, most of these textures exist at low temperatures which is an issue for these applications. This thesis studies room temperature topological magnetic materials using Chromium telluride (CrTe2) and iron gallium telluride (Fe3GaTe2) as a model system via a combination of single-crystal synthesis, experimental structural, and magnetic characterization. The scientific knowledge gained by this work will be useful in designing unique topological textures beyond traditional Skyrmions to merons, bi-skyrmions, etc. which would be useful in improving energy-efficient storage solutions and advancing computational technologies for the future.

Details

Contributors
Date Created
2024
Embargo Release Date
Topical Subject
Resource Type
Language
  • eng
Note
  • Partial requirement for: M.S., Arizona State University, 2024
  • Field of study: Mechanical Engineering

Additional Information

English
Extent
  • 82 pages
Open Access
Peer-reviewed

Fundamentals of Liquid Metal Composites and Emulsions

Description
Room temperature liquid metals (LM) are materials that have metallic properties, including high thermal and electrical conductivity along with fluid characteristics. In recent years, LMs have found wide use in biomaterials, soft robotics, wearable electronics, etc. However, commercial applications of

Room temperature liquid metals (LM) are materials that have metallic properties, including high thermal and electrical conductivity along with fluid characteristics. In recent years, LMs have found wide use in biomaterials, soft robotics, wearable electronics, etc. However, commercial applications of LMs have been restricted due to LM’s high reactivity towards other metals (often causing metal embrittlement), high density, low viscosity, and high surface tension that make high-volume and repeatable device fabrication challenging. This thesis investigates methods to enhance the properties of liquid metals through the incorporation of solid particles and secondary fluids to create LM composites and LM emulsions. The focus is on altering physical properties such as density and viscosity by introducing solid particles into the LM to form LM composites, further allowing for the mixing of secondary fluids to create fluid-in-LM emulsions. The research examines the influence of solid particle volume, size, shape, mixing time, and methods on the structure and properties of the resulting LM composites. Significant findings include the observation of a drop in densities, indicating the addition of air along with solid particles in LM, leading to the conclusion that LM composites contain solid and fluidic components. The study also explores the creation of fluid-in-LM emulsions using silicone oil as the fluid and LM-SiO2 composites and LM-Ag composites, with a focus on the influence of solid particles on the viscosity of the composite and their interaction with the viscosity of the secondary fluid. Overall, this research provides insights into creating LM composites with a more uniform structure and forming desired emulsions, contributing to the understanding of manipulating the properties of liquid metals for various industry-relevant applications.

Details

Contributors
Date Created
2024
Resource Type
Language
  • eng
Note
  • Partial requirement for: Ph.D., Arizona State University, 2024
  • Field of study: Chemical Engineering

Additional Information

English
Extent
  • 101 pages
Open Access
Peer-reviewed

Enabling Systems for Energy Transitions

Description
Achieving a zero net emissions economy in line with science-based climate goals requires coordinated technical efforts at an unprecedented scale and pace. This work identifies and addresses high impact gaps in systems and tools needed to facilitate decision-making analyses, with

Achieving a zero net emissions economy in line with science-based climate goals requires coordinated technical efforts at an unprecedented scale and pace. This work identifies and addresses high impact gaps in systems and tools needed to facilitate decision-making analyses, with a focus on optimization in the context of California’s building energy transition programs. To utilize waste heat from a concentrating solar power tower to deliver process or comfort cooling, technology options are compared across a range of ambient temperatures with each technology being optimized at each design point. Tools for modeling sorption cooling cycles are developed that lower the barrier to entry and enable near real-time design iteration and optimization. An analysis of dual fuel space heating technology potential demonstrates the impact of adopting a connected and optimized control strategy on the operating cost and emissions reduction tradeoff. Based on experience with these analyses, additional discussion points to gaps required to support further optimization analyses and faster iteration of calculation tools used in the regulated energy efficiency industry.

Details

Contributors
Date Created
2024
Resource Type
Language
  • eng
Note
  • Partial requirement for: Ph.D., Arizona State University, 2024
  • Field of study: Mechanical Engineering

Additional Information

English
Extent
  • 204 pages
Open Access
Peer-reviewed

Optimizing Pin Fin Shapes In a Heat Sink: Investigating The Impact of Genetic Algorithm Parameters

Description
This research aims to identify optimal pin fin shapes that minimize flow pressuredrop and maximize heat transfer performance while investigating the influence of genetic algorithm (GA) parameters on these shapes. The primary goal is to discover innovative pin fin configurations through the

This research aims to identify optimal pin fin shapes that minimize flow pressuredrop and maximize heat transfer performance while investigating the influence of genetic algorithm (GA) parameters on these shapes. The primary goal is to discover innovative pin fin configurations through the use of a GA, moving away from traditional circular cylindrical designs. The study also examines GA parameters, including population size, generation size, selection methods, crossover rates, tournament size, and elite counts. A physical condition considered in this study is a rectangular channel with a square cross-section integrated with 10 pin fins, operating at a Reynolds number of 2316, and subjected to a heat flux of 5 W/cm2 at the bottom surface. Overall, the research seeks to enhance the energy efficiency of a liquid cooling system, with potential applications in the thermal management of computing devices. By enabling operating at significantly lower power, the optimized cooling system promises to reduce energy consumption and operational costs.

Details

Contributors
Date Created
2024
Resource Type
Language
  • eng
Note
  • Partial requirement for: M.S., Arizona State University, 2024
  • Field of study: Aerospace Engineering

Additional Information

English
Extent
  • 85 pages
Open Access
Peer-reviewed

Thermal Modeling of Wide and Ultra-wide Bandgap Materials and Devices Through Cellular Monte Carlo

Description
An efficient thermal solver is available in the CMC that allows modeling self-heating in the electrical simulations, which treats phonons as flux and solves the energy balance equation to quantify thermal effects. Using this solver, thermal simulations were performed on

An efficient thermal solver is available in the CMC that allows modeling self-heating in the electrical simulations, which treats phonons as flux and solves the energy balance equation to quantify thermal effects. Using this solver, thermal simulations were performed on GaN-HEMTs in order to test effect of gate architectures on the DC and RF performance of the device. A Π- gate geometry is found to suppress 19.75% more hot electrons corresponding to a DC power of 2.493 W/mm for Vgs = -0.6V (max transconductance) with respect to the initial T-gate. For the DC performance, the output current, Ids is nearly same for each device configuration over the entire bias range. For the RF performance, the current gain was evaluated over a frequency range 20 GHz to 120 GHz in each device for both thermal (including self-heating) and isothermal (without self-heating). The evaluated cutoff frequency is around 7% lower for the thermal case than the isothermal case. The simulated cutoff frequency closely follows the experimental cutoff frequency. The work was extended to the study of ultra-wide bandgap material (Diamond), where isotope effect causes major deterioration in thermal conductivity. In this case, bulk phonons are modeled as semiclassical particles solving the nonlinear Peierls - Boltzmann transport equation with a stochastic approach. Simulations were performed for 0.001% (ultra-pure), 0.1% and 1.07% isotope concentration (13C) of diamond, showing good agreement with the experimental values. Further investigation was performed on the effect of isotope on the dynamics of individual phonon branches, thermal conductivity and the mean free path, to identify the dominant phonon branch. Acoustic phonons are found to be the principal contributors to thermal conductivity across all isotope concentrations with transverse acoustic (TA2) branch is the dominant branch with a contribution of 40% at room temperature and 37% at 500K. Mean free path computations show the lower bound of device dimensions in order to obtain maximum thermal conductivity. At 300K, the lowest mean free path (which is attributed to Longitudinal Optical phonon) reduces from 24nm to 8 nm for isotope concentration of 0.001% and 1.07% respectively. Similarly, the maximum mean free path (which is attributed to Longitudinal Acoustic phonon) reduces from 4 µm to 3.1 µm, respectively, for the same isotope concentrations. Furthermore, PETSc (Portable, Extensible Toolkit for Scientific Computation) developed by Argonne National Lab, was included in the existing Cellular Monte Carlo device simulator as a Poisson solver to further extend the capability of the simulator. The validity of the solver was tested performing 2D and 3D simulations and the results were compared with the well-established multigrid Poisson solver.

Details

Contributors
Date Created
2024
Topical Subject
Resource Type
Language
  • eng
Note
  • Partial requirement for: Ph.D., Arizona State University, 2024
  • Field of study: Electrical Engineering

Additional Information

English
Extent
  • 131 pages
Open Access
Peer-reviewed

Multi-Day Thermochemical Energy Storage

Description
Energy storage technologies are essential to overcome the temporal variability in renewable energy. The primary aim of this thesis is to develop reactor solutions to better analyze the potential of thermochemical energy storage (TCES) using non-stoichiometric metal oxides, for the

Energy storage technologies are essential to overcome the temporal variability in renewable energy. The primary aim of this thesis is to develop reactor solutions to better analyze the potential of thermochemical energy storage (TCES) using non-stoichiometric metal oxides, for the multi-day energy storage application. A TCES system consists of a reduction reactor and an insulated MOx storage bin. The reduction reactor heats (to ~ 1100 °C) and partially reduces the MOx, thereby adding sensible and chemical energy (i.e., charging it) under reduced pO2 environments (~10 Pa). Inert gas removes the oxygen generated during reduction. The storage bin holds the hot and partially reduced MOx (typically particles) until it is used in an energy recovery device (i.e., discharge). Irrespective of the reactor heat source (here electrical), or the particle-inert gas flows (here countercurrent), the thermal reduction temperature and inert gas (here N2) flow minimize when the process approaches reversibility, i.e., operates near equilibrium. This study specifically focuses on developing a reduction reactor based on the theoretical considerations for approaching reversibility along the reaction path. The proposed Zigzag flow reactor (ZFR) is capable of thermally reducing CAM28 particles at temperatures ~ 1000 °C under an O2 partial pressure ~ 10 Pa. The associated analytical and numerical models analyze the reaction equilibrium under a real (discrete) reaction path and the mass transfer kinetic conditions necessary to approach equilibrium. The discrete equilibrium model minimizes the exergy destroyed in a practical reactor and identifies methods of maximizing the energy storage density () and the exergetic efficiency. The mass transfer model analyzes the O2 N2 concentration boundary layers to recommend sizing considerations to maximize the reactor power density. Two functional ZFR prototypes, the -ZFR and the -ZFR, establish the proof of concept and achieved a reduction extent, Δδ = 0.071 with CAM28 at T~950 °C and pO2 = 10 Pa, 7x higher than a previous attempt in the literature. The -ZFR consistently achieved  > 100 Wh/kg during >10 h. runtime and the -ZFR displayed an improved  = 130 Wh/kg during >5 h. operation with CAM28. A techno-economic model of a grid-scale ZFR with an associated storage bin analyzes the cost of scaling the ZFR for grid energy storage requirements. The scaled ZFR capital costs contribute < 1% to the levelized cost of thermochemical energy storage, which ranges from 5-20 ¢/kWh depending on the storage temperature and storage duration.

Details

Contributors
Date Created
2023
Resource Type
Language
  • eng
Note
  • Partial requirement for: Ph.D., Arizona State University, 2023
  • Field of study: Mechanical Engineering

Additional Information

English
Extent
  • 160 pages
Open Access
Peer-reviewed

Direct Ink Written Luminous Monoliths for Hydrogen Sulfide Photocatalysis

Description
The conversion of H2S enables the recycling of a waste gas into a potential source of hydrogen at a lower thermodynamic energy cost as compared to water splitting. However, studies on the photocatalytic decomposition of H2S focus on traditional deployment

The conversion of H2S enables the recycling of a waste gas into a potential source of hydrogen at a lower thermodynamic energy cost as compared to water splitting. However, studies on the photocatalytic decomposition of H2S focus on traditional deployment of catalyst materials to facilitate this conversion, and operation only when a light source is available. In this study, the efficacy of Direct Ink Written (DIW) luminous structures for H2S conversion has been investigated, with the primary objective of sustaining H2S conversion when a light source has been terminated. Additionally, as a secondary objective, improving light distribution within monoliths for photocatalytic applications is desired. The intrinsic illumination of the 3D printed monoliths developed in this work could serve as an alternative to monolith systems that employ light transmitting fiber optic cables that have been previously proposed to improve light distribution in photocatalytic systems. The results that were obtained demonstrate that H2S favorable adsorbents, a wavelength compatible long afterglow phosphor, and a photocatalyst can form viscoelastic inks that are printable into DIW luminous monolithic contactors. Additionally, rheological, optical and porosity analyses conducted, provide design guidelines for future studies seeking to develop DIW luminous monoliths from compatible catalyst-phosphor pairs. The monoliths that were developed demonstrate not only improved conversion when exposed to light, but more significantly, extended H2S conversion from the afterglow of the monoliths when an external light source was removed. Lastly, considering growing interests in attaining a global circular economy, the techno-economic feasibility of a H2S-CO2 co-utilization plant leveraging hydrogen from H2S photocatalysis as a feed source for a downstream CO2 methanation plant has been assessed. The work provides preliminary information to guide future chemical kinetic design characteristics that are important to strive for if using H2S as a source of hydrogen in a CO2 methanation facility.

Details

Contributors
Date Created
2023
Embargo Release Date
Resource Type
Language
  • eng
Note
  • Partial requirement for: Ph.D., Arizona State University, 2023
  • Field of study: Mechanical Engineering

Additional Information

English
Extent
  • 154 pages
Open Access
Peer-reviewed

Development and Evaluation of a Laboratory Water Pump Simulation with Measurement Uncertainty for Enhanced Learning

Description
Expedited by the ongoing effects of the Covid-19 pandemic and the expanding portfolio of Arizona State University's online degree programs, this study undertakes the task of enriching the “Experimental Mechanical Engineering” course within ASU's online Bachelor of Mechanical Engineering curriculum.

Expedited by the ongoing effects of the Covid-19 pandemic and the expanding portfolio of Arizona State University's online degree programs, this study undertakes the task of enriching the “Experimental Mechanical Engineering” course within ASU's online Bachelor of Mechanical Engineering curriculum. This thesis outlines the development of simulations accurately mirroring the characteristics and functionalities of water pump laboratory experiments, which previously necessitated on-site, group-based participation. The goal is for these simulations to serve as digital twins of the original equipment, allowing students to examine fundamental mechanical principles like the Bernoulli equation and Affinity Laws in a virtual, yet realistic setting. Furthermore, the simulations are designed to accommodate uncertainty calculations, replicating the instrument error (i.e., bias and precision uncertainty) inherent in the original water pump units. The methodology of this simulation design predominantly involves the use of MATLAB SimScape, chosen for its configurability and simplicity, with modifications made to match the original experiment data. Then, subsequent analysis of results between the simulation and experiment is conducted to facilitate the validation process. After executing the full laboratory procedure using the simulations, they displayed rapid operation and produced results that remained within boundaries of experimental uncertainty, it also faces several challenges, such as the inability to simulate the pump cavitation effect and the lack of animation. Future research should focus on addressing these limitations, thereby enhancing the model’s precision and extending its functionality to provide better visualization capabilities and exploration of pump cavitation effects. Furthermore, students’ feedback needs to be collected, since it is essential to assess and validate the effectiveness of this instructional approach.

Details

Contributors
Date Created
2023
Resource Type
Language
  • eng
Note
  • Partial requirement for: M.S., Arizona State University, 2023
  • Field of study: Mechanical Engineering

Additional Information

English
Extent
  • 101 pages
Open Access
Peer-reviewed

Direct Convection Correction for Cylindrical Radiometer Measurement

Description
Human exposure to extreme heat is becoming more prevalent due to increasing urbanization and changing climate. In many extreme heat conditions, thermal radiation (from solar to emitted by the surrounding) is a significant contributor to heating the body, among other

Human exposure to extreme heat is becoming more prevalent due to increasing urbanization and changing climate. In many extreme heat conditions, thermal radiation (from solar to emitted by the surrounding) is a significant contributor to heating the body, among other modes of heat transfer. Therefore, accurately measuring radiative heat flux on a human body is becoming increasingly important for calculating human thermal comfort and heat safety in extreme conditions. Most often, radiant heat exchange between the human body and surroundings is quantified using mean radiant temperature, T_mrt. This value is commonly measured using globe or cylindrical radiometers. It is based on radiation absorbed by the surface of the radiometer, which can be calculated using a surface energy balance involving both convection and emitted radiation at steady state. This convection must be accounted for and is accomplished using a traditional heat transfer coefficient correlation with measured wind speed. However, the utilized correlations are based on wind tunnel measurements and do not account for any turbulence present in the air. The latter can even double the heat transfer coefficient, so not accounting for it can introduce major errors in T_mrt. This Thesis focuses on the development, and testing of a cost-effective heated cylinder to directly measure the convection heat transfer coefficient in field conditions, which can be used for accounting convection in measuring T_mrt using a cylindrical radiometer. An Aluminum cylinder of similar dimensions as that of a cylindrical radiometer was heated using strip heaters, and the surface temperature readings were recorded to estimate the convection heat transfer coefficient, h. Various tests were conducted to test this concept. It was observed that heated cylinders take significantly less time to reach a steady state and respond to velocity change quicker than existing regular-sized globe thermometers. It was also shown that, for accurate estimation of h, it is required to measure the outer surface temperature than the center temperature. Furthermore, the value calculated matches well in range with classic correlations that include velocity, showing proof of concept.

Details

Contributors
Date Created
2023
Resource Type
Language
  • eng
Note
  • Partial requirement for: M.S., Arizona State University, 2023
  • Field of study: Aerospace Engineering

Additional Information

English
Extent
  • 55 pages
Open Access
Peer-reviewed