There is growing interest to use supercritical carbon dioxide (sCO2) as a working fluid in thermal management applications. This study investigates the thermal-hydraulic performance of microchannel heat sinks as a function of flow channel geometry and orientation at operating conditions representative of electronics cooling applications. Three different experimental test sections,...
Supercritical carbon dioxide (sCO2) experiences a drastic change in its thermophysical properties near the thermodynamic critical point. A non-linear thermophysical property variation can influence the heat transfer behavior of sCO2 which is not predicted well by conventional single phase heat transfer theory. This can become a major hindrance in the...
In climate regions with large seasonal variations in solar radiation, such as the Pacific Northwest of the United States, a solar thermal energy collector might not economically satisfy year-round domestic water heating demands, requiring an auxiliary unit, such as a natural gas-fired water heater. Previous studies have shown that the...
Membrane based heat pumps systems have attracted the attention of many research groups as a potentially more environmentally friendly alternative to vapor compression systems for space cooling. Several prototype systems have been developed, with reported claims of Energy Efficiency Ratios (EER) approaching 26. At present, no detailed analysis is publicly...
The advancement of additive manufacturing enables significantly greater freedom of design compared to conventional techniques. Of significant interest is the potential improvements in the design of cold plates and heat sinks for electronics cooling. Greater design freedom could enable new designs that reduce thermal resistance and hydraulic resistance, enabling the...
Concentrated solar power (CSP) plants have the potential to provide 24 h, renewable electricity. Current CSP systems have high capital and operational costs which makes the levelized cost of electricity uncompetitive with conventional techniques. Recent experimental research has shown the potential of small unit cells (up to 2 × 2 cm) containing micropin arrays...
Qualitative two-phase flow regime data are obtained from high-speed visualization of condensing flows of R-134a at mass fluxes from 75 to 150 kg m−2 s−1 and quality from 0.1 to 0.8 in square microchannels (DH = 0.84 mm) cooled from a single side. Superheated R-134a is distributed into multiple parallel microchannels and then partially condensed, using...
The role of volumetric energy density on the microstructural evolution, texture and mechanical properties of 304L stainless steel parts additively manufactured via selective laser melting process is investigated. 304L is chosen because it is a potential candidate to be used as a matrix in a metal matrix composite with nanoparticles...
Vortical structures are the driving mechanism of transition to turbulence in porous media requiring adequately resolved observations along with analysis of the scale and energy of flow within the pores. Of specific interest is to understand the vortex dynamics, energy, and turbulent mixing and transport properties in the scale of...
Energy recovery ventilators (ERVs) are an effective way to reduce energy consumption in buildings while satisfying ventilation standards. As membrane technology and manufacturing methods improve, membrane based ERVs are seeing increased market penetration. In the present study, the feasibility of membrane ERV designed to fit in a commercial building wall...
Concentrated solar power (CSP) plants have the potential to reduce the consumption of nonrenewable resources and greenhouse gas emissions in electricity production. In CSP systems, a field of heliostats focuses solar radiation on a central receiver, and energy is then transferred to a thermal power plant at high temperature. However,...
Waste heat driven ammonia/water Kalina cycles have shown promise for improving the efficiency of electricity production from low-temperature reservoirs (T < 150 °C). However, there has been limited application of these systems to utilize widely available, disperse, waste heat streams for smaller scale power production (1–10 kWe). Factors limiting increased deployment of these...
A novel thermal management approach is explored, which uses supercritical carbon dioxide (sCO2) as a working fluid to manage extreme heat fluxes in electronics cooling applications. In the pseudocritical region, sCO2 has extremely high volumetric thermal capacity, which can enable operation with low pumping requirements, and without the potential for...
Heat transfer coefficients and frictional pressure drop values are experimentally measured during condensation of R134a and its proposed low global warming potential (GWP) replacement, R450A. R450A is a non-flammable zeotropic mixture of R134a and R1234ze (42/58% by mass). Experiments were conducted in a horizontal tube (ID = 4.7 mm) for...
Implementing multicomponent diffusion in numerical combustion studies is computationally expensive due to the challenges involved in computing diffusion coefficients. As a result, mixture-averaged diffusion treatments or simpler methods are used to avoid these costs. However, the accuracy and appropriateness of the mixture-averaged diffusion model has not been verified for three-dimensional...
Teamwork has become a popular operational strategy applied as part of workforce management plans in manufacturing and service industries. Teamwork has been commonly used in organizations to pursue different goals such as increase business operations agility, boost company productivity, improve quality in operations, increase company flexibility, promote collaborative learning, hasten...
Gasoline direct injection engines, with downsized boosted technology, present a promising option for enhancing power density and reducing fuel consumption for next-generation engine designs to meet stringent fuel economy and emission standards. However, these developments in the low-speed and high-load operating regime are challenged by the occurrence of a new...
This data contains results from direct numerical simulations of three-dimensional, premixed, hydrogen/air flames, using the mixture-averaged diffusion model. We performed the simulations using the finite-difference code NGA; simulation details are described completely in the associated article.
Digital Human Modeling (DHM) is a computational design tool that allows designers to use virtual prototypes of design for exploring ergonomics requirements. DHM brings in the advantage of reducing the time and finances committed to building the physical prototypes as well as minimizing the efforts put on performing human subject...
As carbon emissions are negatively impacting ecosystems across the globe, researchers are in a race against time to provide cleaner and more eÿcient power. Detonation engines can help meet the increasing demands for cleaner and more eÿcient power generation by providing an alternative means to use oxy-fuel combustion for carbon...
Moving mixed-model assembly lines are used by many companies to assemble multiple model types of a particular product. A moving assembly line consists of a material movement system that moves jobs at a constant velocity across a series of workstations. The variation in the work content of jobs at workstations...
The orb web is a multipurpose structure---serving as a home for its inhabitant spider, as a prey capture device, and as a physical extension of the spider’s sensing abilities. Biologists are particularly interested in the spider’s ability to locate prey trapped in its web by sensing the vibrations induced from...
The myriad of problems facing the world today are increasingly complex, dynamic, and transcend multiple domains necessitating the need for an equally complex and trans-disciplinary approach to solve these problems. Systems thinking promises to provide the skills necessary for all citizens of the world, not just the experts, to handle...
Topology optimization (TO) is a mathematical method to find the optimal size, shape and connectivity of a domain under specified conditions, and has had many applications in engineering design. However, challenges remain in realizing TO as an effective design tool for many design situations. Uncertainty is ubiquitous in nature and...
This dissertation details the application of digital image correlation (DIC) in novel methods for mechanical testing and shape characterization. The first usage manifested in the development of a novel composite test specimen that provided the ability to characterize the matrix compression energy release rate at initiation and subsequent crack propagation....
This study seeks to determine the effect of instructional design and emotional state on performance, considering interest and attention as mediators. To identify this effect, a Structural Equation Model (SEM) is applied to analyze individual performance based on five variables: information representation, emotional state, pupil size, alpha power, and task...
Manufacturing process design (MPD) represents a design-oriented approach to manufacturing engineering. In this dissertation, Haynes 230 (H230), a solid solution-strengthened Ni-based superalloy, was chosen to meet the material requirements of a microchannel solar receiver (MSR) needed to increase the efficiency and reduce the cost of solar thermal power generation. An...
The behavior of the thin liquid film formed between a bubble and hydrophobic membrane is of high interest in applications where separating two-phase mixtures is beneficial. One such application is in-situ vapor extraction heat sinks. In these systems, high heat transfer rates are accomplished by taking advantage of the high...
The rising global trend to reduce dependence on fossil fuels has provided significant motivation toward the development of alternative energy conversion methods and new technologies to improve their efficiency. Recently, oscillating energy harvesters have shown promise as highly efficient and scalable turbines, which can be implemented in areas where traditional...
Microchannel high temperature recuperators have the advantage of higher heat transfer coefficients and lower size and weight than traditional high temperature recuperators. However, the industrial application of microchannel recuperators are restricted by the high cost of photochemical machining and diffusion bonding. The objective of this paper is to introduce a...
In order to solve some classic problems in traditional topology optimization, such as unknown material distribution, checker-boarding and curse of dimensionality, this thesis introduces a new method to construct a mechanical structure that can reduce mass and increase stiffness. It uses a graph to represent the skeleton of a structure....
Specific energy, defined as the energy consumed by per unit volumetric removal rate, is one of the key metrics used for evaluating the environmental performance of a machining process. Grinding is a traditional machining process, characterized by high specific energy and poor environmental performance. Growing global concerns about climate change...
The aviation industry is pushing for better fuels and gas turbine engines for several reasons: cost, emissions, and to a lesser extent high-altitude relights. One aspect that research has been focused on to help reduce costs, emissions and better understand high-altitude relights is studying the combustion behavior of the fuel...
Breakthroughs in heat sink design are now limited by conventional manufacturing techniques which can only produce basic fin shapes with homogenous surface structuring. Additive Manufacturing (AM) is a potential disruptive technology for heat sink design and other convective heat transfer solutions, as surface properties can be directionally varied to maximize...
This thesis presents accurate and time-optimal smooth reference trajectory generation techniques for manufacturing equipment such as high-speed machine tools (MT) and industrial robots (IR). Typical machining tool-paths for MTs and IRs are defined as a series of discrete linear moves. Although Point-to-Point (P2P) feed motion can be generated by interpolating...
The fuzzy front end of engineering design can present a difficult challenge, and as such, recent engineering design research has focused on guiding and influencing the way a designer ideates. Early ideation can be especially difficult when attempting to integrate specific design objectives in product design, called Design for X...
Sustainability has become an unprecedented priority in global manufacturing due to the growing concerns over issues such as an aging workforce, environmental degradation, and public health. The simultaneous consideration of the economic, environmental, and social aspects – often referred to as the “three pillars of sustainability” – is crucial to...
In a seminal paper published in 1982, scientist have warned that humanity was pushing earth’s ecosystems beyond their capacities to support the web of life. One response to the concern was outlined by NASA with its vision for advanced fixed wing transport aircraft to be environmentally compatible and have revolutionary...
This research presents a methodology to identify and analyze human-system interactions, and their potential failure modes using a functional decomposition approach during the early system design stage.
The fundamental research contribution of this work is the development of a framework to identify associations between physical user-product interactions, generic human errors...
Awareness and implementation of process improvement strategies, like Six Sigma, Total Quality Management, and Lean Management have increased since the 1980s. In more recent history, lean management thinking has shown its significance in the manufacturing world. Kuwait, being a country in which its whole dependence is on revenues of oil...
As CAD tools become more sophisticated, engineers are able to more easily create complex part geometries with minimal mass given strength and stiffness requirements. However, these complex part geometries can be difficult to subtractively manufacture, which consequently increases manufacturing cost and production time. This thesis presents a method independent of...
With the widespread replacement of aluminum with composite materials, particularly in aircraft structures, the lack of comprehensive understanding of these materials is unsettling. The complex nature of these materials, with respect to isotropic aluminum, makes the prediction of their mechanical response equally complex. The failure of carbon fiber reinforced plastic...
Selective laser melting (SLM) is an additive manufacturing (AM) process that uses a laser beam to melt metal powder as it is spread onto the build surface using a roller or scraper, followed by rapid solidification to manufacture a 3D component, one layer at a time.
In SLM process, density...
This work develops the Global Formula Racing computational fluid dynamics (CFD) model in StarCCM+ to allow for vehicle attitude studies to be ran to evaluate Formula Student (FS) vehicle aerodynamic loads. Attitudes that this model allows to be studied include roll, pitch, yaw, heave, tire angle, and vehicle speed. The...
Clean cooking technologies and fuels have been cited as a viable way to slow climate change and reduce the health and environmental impacts associated with traditional cooking devices used by 40% of the world. While engineers in the Design for Development sector have created hundreds of stove designs that perform...
Clean technologies can address multiple challenges associated with climate change, environmental protection, and human health. However, the impact desired by introduction of such technologies is achievable only if new options effectively replace inefficient, conventional practices. This ‘design for adoption’ requires understanding of user motivations, associated beliefs, context of use, and...
In general, making optimal decisions is a never ending challenge that decision makers face. A comprehensive model that integrates decisions at all three levels of decision making (i.e., strategic, tactical, and operational) can help the decision maker to find solutions that best serve the organization's performance. However, as organizations expand...
The amorphous to crystalline phase change is of great interest for the production and operation of phase change memory and germanium electronic devices. Phase change memory relies on the ability to differentiate between differences in optical or electrical properties between the amorphous and crystalline phases of a single material. Amorphous...
In this research, the comparative performance of permutation and non-permutation schedules is investigated in an assembly flow shop (AFS) with shift production, where a limited buffer storage is available between two machines. Most of the traditional scheduling problems consider continuous production, i.e., production occurs for 24 hours (3 * 8-hour...
Complex engineered systems design is a collaborative activity. To design a system, experts from the relevant disciplines must work together to create the best overall system from their individual components. This situation is analogous to a multiagent system in which agents solve individual parts of a larger problem in a...