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Description
Recent literature indicates potential benefits in microchannel cooling if an inlet orifice is used to suppress pressure oscillations that develop under two-phase conditions. This study investigates the costs and benefits of using an adjustable microchannel inlet orifice. The focus is on orifice effect during steady-state boiling and critical heat flux (CHF) in the channels using R134a in a pumped refrigerant loop (PRL). To change orifice size, a dam controlled with a micrometer was placed in front of 31 parallel microchannels. Each channel had a hydraulic diameter of 0.235 mm and a length of 1.33 cm. For steady state two-phase conditions, mass fluxes of 300 kg m-2 s-1 and 600 kg m-2 s-1were investigated. For orifice sizes with a hydraulic diameter to unrestricted hydraulic diameter (Dh:Dh,ur) ratio less than 35 percent, oscillations were reduced and wall temperatures fell up to 1.5 °C. Critical heat flux data were obtained for 7 orifice sizes with mass fluxes from 186 kg m-2 s-1 to 847 kg m-2 s-1. For all mass fluxes and inlet conditions tested, CHF values for a Dh:Dh,ur ratio of 1.8 percent became increasingly lower (up to 37 W cm-2 less) than those obtained with larger orifices. An optimum orifice size with Dh:Dh,ur of 35 percent emerged, offering up to 5 W cm-2 increase in CHF over unrestricted conditions at the highest mass flux tested, 847 kg m-2 s-1. These improvements in cooling ability with inlet orifices in place under both steady-state and impending CHF conditions are modest, leading to the conclusion that inlet orifices are only mildly effective at improving heat transfer coefficients. Stability of the PRL used for experimentation was also studied and improved. A vapor compression cycle's (VCC) proportional, integral, and derivative controller was found to adversely affect stability within the PRL and cause premature CHF. Replacing the VCC with an ice water heat sink maintained steady pumped loop system pressures and mass flow rates. The ice water heat sink was shown to have energy cost savings over the use of a directly coupled VCC for removing heat from the PRL.
ContributorsOdom, Brent A (Author) / Phelan, Patrick E (Thesis advisor) / Herrmann, Marcus (Committee member) / Trimble, Steve (Committee member) / Tasooji, Amaneh (Committee member) / Holcomb, Don (Committee member) / Arizona State University (Publisher)
Created2012
Description
This work demonstrates a capable reverse pulse deposition methodology to influence gap fill behavior inside microvia along with a uniform deposit in the fine line patterned regions for substrate packaging applications. Interconnect circuitry in IC substrate packages comprises of stacked microvia that varies in depth from 20µm to 100µm with an aspect ratio of 0.5 to 1.5 and fine line patterns defined by photolithography. Photolithography defined pattern regions incorporate a wide variety of feature sizes including large circular pad structures with diameter of 20µm - 200µm, fine traces with varying widths of 3µm - 30µm and additional planar regions to define a IC substrate package. Electrodeposition of copper is performed to establish the desired circuit. Electrodeposition of copper in IC substrate applications holds certain unique challenges in that they require a low cost manufacturing process that enables a void-free gap fill inside the microvia along with uniform deposition of copper on exposed patterned regions. Deposition time scales to establish the desired metal thickness for such packages could range from several minutes to few hours. This work showcases a reverse pulse electrodeposition methodology that achieves void-free gap fill inside the microvia and uniform plating in FLS (Fine Lines and Spaces) regions with significantly higher deposition rates than traditional approaches. In order to achieve this capability, systematic experimental and simulation studies were performed. A strong correlation of independent parameters that govern the electrodeposition process such as bath temperature, reverse pulse plating parameters and the ratio of electrolyte concentrations is shown to the deposition kinetics and deposition uniformity in fine patterned regions and gap fill rate inside the microvia. Additionally, insight into the physics of via fill process is presented with secondary and tertiary current simulation efforts. Such efforts lead to show “smart” control of deposition rate at the top and bottom of via to avoid void formation. Finally, a parametric effect on grain size and the ensuing copper metallurgical characteristics of bulk copper is also shown to enable high reliability substrate packages for the IC packaging industry.
ContributorsGanesan, Kousik (Author) / Tasooji, Amaneh (Thesis advisor) / Manepalli, Rahul (Committee member) / Alford, Terry (Committee member) / Chan, Candace (Committee member) / Arizona State University (Publisher)
Created2018
Targeting Tumors: Inclusion of Functional Groups on Ion-Containing Block Copolymers to Combat Cancer
Description
This research attempts to determine the most effective method of synthesizing a peptide such that it can be utilized as a targeting moiety for polymeric micelles. Two melanoma-associated peptides with high in vitro and in vivo binding affinity for TNF receptors have been identified and synthesized. Matrix Assisted Laser Desorption/Ionization-Time of Flight Mass Spectrometry (MALDI-ToF) was used to help verify the structure of both peptides, which were purified using Reversed-Phase High Performance Liquid Chromatography (RP-HPLC). The next steps in the research are to attach the peptides to a micelle and determine their impact on micelle stability.
ContributorsMoe, Anna Marguerite (Author) / Green, Matthew (Thesis director) / Jones, Anne (Committee member) / Sullivan, Millicent (Committee member) / Chemical Engineering Program (Contributor) / School of International Letters and Cultures (Contributor) / Sandra Day O'Connor College of Law (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
The mechanisms of extracellular respiration in Geobacter sulfurreducens, commonly considered to be a model organism for anode respiration, are yet to be completely understood. The interplay between electron and proton transport especially could be a key to gaining further insights. One way to investigate the mechanisms of extracellular respiration under varying environmental conditions is by analyzing the electrochemical response of the biofilm with respect to pH, buffer concentrations, and acetate concentrations. I seek to increase the understanding of the electrochemical response of the G. sulfurreducens biofilm through electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques in concert with chronoamperometry. I used Geobacter sulfurreducens PCA biofilms in single-chamber electrochemical cells (approximately 100 mL volume) with a small gold working electrode (3.14 mm2). I observed limitations in the initial methods used for media replacement. I tracked changes in the CV data, such as EKA (midpoint potential), as a function of pH and buffer concentration. The media replacement method developed demonstrates success in pH experiments that will be transferrable to other environmental conditions to study electron transport. The experiments revealed that the clarity of data collected is dependent on the quality of the biofilm. A high quality biofilm is characterized by a high current density and normal growth behavior. The general trends seen in these experiments are that as pH increases the potential decreases, and as buffer concentration increases the potential decreases and pH increases. Acetate-free conditions in the reactor were unable to be achieved as characterized by non-zero current densities in the acetate-free experiments.
ContributorsHolzer, Denton Gene (Author) / Torres, Cesar (Thesis director) / Popat, Sudeep (Committee member) / Yoho, Rachel (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
Lithium-ion batteries are the predominant source of electrical energy storage for most portable electronics applications, including hybrid/electric vehicles, laptops, and cellular phones. However, these batteries pose safety concerns due to their flammability and tendency to violently ignite upon short circuiting or failing. Solid electrolytes are a current research development aimed at reducing the flammability and reactivity of lithium batteries. The compound Li7La3Zr2O12, or LLZO, exhibits satisfactory ionic conductivity in the cubic phase, which is normally synthesized via doping with Al. It has recently been discovered that synthesizing nanostructured LLZO can stabilize the cubic phase without the need for doping. Here nanostructured LLZO was formed using templating on various cellulosic fibers, including cotton fibers, printer paper, filter paper, and nanocellulose fibrils followed by calcination at 700-800 °C. The effect of templating material, calcination temperature, calcination time, and heating ramp rate on LLZO phase and morphology was thoroughly investigated. Templating was determined to be an effective method for controlling the LLZO size and morphology, and most templating experiments resulted in LLZO fibers or ligaments similar in size and morphology to the original template material. A systematic study on the various experimental parameters was performed, concluding that low calcination time and low ramp rate favored smaller ligament formation. Further, it was verified that cubic phase stabilization occurred for LLZO with ligaments of less than 1 micron on average without the use of doping. This research provides more information regarding the size dependence on cubic LLZO stabilization that has not been previously investigated in detail.
ContributorsGordon, Zachary Daniel (Author) / Chan, Candace K. (Thesis director) / Lin, Jerry (Committee member) / Barrett, The Honors College (Contributor) / School of Mathematical and Statistical Sciences (Contributor) / Chemical Engineering Program (Contributor)
Created2015-05
Description
The goal of this research project is to create a mixed matrix membrane that can withstand very acidic environments but still be used to purify water. The ultimate goal of this membrane is to be used to purify urine both here on Earth and in space. The membrane would be able to withstand these harsh conditions due the incorporation of a resilient impermeable polymer layer that will be cast above the lower hydrophilic layer. Nanoparticles called zeolites will act as a water selective pathway through this impermeable layer and allow water to flow through the membrane. This membrane will be made using a variety of methods and polymers to determine both the cheapest and most effective way of creating this chemical resistant membrane. If this research is successful, many more water sources can be tapped since the membranes will be able to withstand hard conditions. This document is primarily focused on our progress on the development of a highly permeable polymer-zeolite film that makes up the bottom layer of the membrane. Multiple types of casting methods were investigated and it was determined that spin coating at 4000 rpm was the most effective. Based on a literature review, we selected silicalite-1 zeolites as the water-selective nanoparticle component dispersed in a casting solution of polyacrylonitrile in N-methylpyrrolidinone to comprise this hydrophilic layer. We varied the casting conditions of several simple solution-casting methods to produce thin films on the porous substrate with optimal film properties for our membrane design. We then cast this solution on other types of support materials that are more flexible and inexpensive to determine which combination resulted in the thinnest and most permeable film.
ContributorsHerrera, Sofia Carolina (Author) / Lind, Mary Laura (Thesis director) / Khosravi, Afsaneh (Committee member) / Hestekin, Jamie (Committee member) / Barrett, The Honors College (Contributor) / Chemical Engineering Program (Contributor)
Created2015-05
Description
In our modern world the source of for many chemicals is to acquire and refine oil. This process is becoming an expensive to the environment and to human health. Alternative processes for acquiring the final product have been developed but still need work. One product that is valuable is butanol. The normal process for butanol production is very intensive but there is a method to produce butanol from bacteria. This process is better because it is more environmentally safe than using oil. One problem however is that when the bacteria produce too much butanol it reaches the toxicity limit and stops the production of butanol. In order to keep butanol from reaching the toxicity limit an adsorbent is used to remove the butanol without harming the bacteria. The adsorbent is a mesoporous carbon powder that allows the butanol to be adsorbed on it. This thesis explores different designs for a magnetic separation process to extract the carbon powder from the culture.
ContributorsChabra, Rohin (Author) / Nielsen, David (Thesis director) / Torres, Cesar (Committee member) / Barrett, The Honors College (Contributor) / Chemical Engineering Program (Contributor)
Created2015-05
Description
One of the primary bottlenecks to chemical production in biological organisms is the toxicity of the chemical. Overexpression of efflux pumps has been shown to increase tolerance to aromatic compounds such as styrene and styrene oxide. Tight control of pump expression is necessary to maximize titers and prevent excessive strain on the cells. This study aimed to identify aromatic-sensitive native promoters and heterologous biosensors for construction of closed-loop control of efflux pump expression in E. coli. Using a promoter library constructed by Zaslaver et al., activation was measured through GFP output. Promoters were evaluated for their sensitivity to the addition of one of four aromatic compounds, their "leaking" of signal, and their induction threshold. Out of 43 targeted promoters, 4 promoters (cmr, mdtG, yahN, yajR) for styrene oxide, 2 promoters (mdtG, yahN) for styrene, 0 promoters for 2-phenylethanol, and 1 promoter for phenol (pheP) were identified as ideal control elements in aromatic bioproduction. In addition, a series of three biosensors (NahR, XylS, DmpR) known to be inducible by other aromatics were screened against styrene oxide, 2-phenylethanol, and phenol. The targeted application of these biosensors is aromatic-induced activation of linked efflux pumps. All three biosensors responded strongly in the presence of styrene oxide and 2-phenylethanol, with minor activation in the presence of phenol. Bioproduction of aromatics continues to gain traction in the biotechnology industry, and the continued discovery of aromatic-inducible elements will be essential to effective pathway control.
ContributorsXu, Jimmy (Author) / Nielsen, David (Thesis director) / Wang, Xuan (Committee member) / School of Life Sciences (Contributor) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
Asymmetric polystyrene-gold composite particles are successfully synthesized alongside core-shell composite particles via a one-step Pickering emulsion polymerization method. Unlike core-shell particles which form in the droplet phase of a stabilized Pickering emulsion, asymmetric particles form via a seeded growth mechanism. These composite particles act as catalysts with higher recyclability than pure gold nanoparticles due to reduced agglomeration. With the addition of N-isopropylacrylamide (NIPAAM) monomers, temperature-responsive asymmetric and core-shell polystyrene/poly(N-isopropylacrylamide)-gold composite particles are also synthesized via Pickering emulsion polymerization. The asymmetric particles have a greater thermo-responsiveness than the core-shell particles due to the increased presence of NIPAAM monomers in the seeded-growth formation. Poly(N-isopropylacrylamide) (PNIPAM)-containing asymmetric particles have tunable rheological and optical properties due to their significant size decrease above the lower critical solution temperature (LCST).
ContributorsRabiah, Noelle Ibrahim (Author) / Dai, Lenore (Thesis director) / Torres, Cesar (Committee member) / Zhang, Mingmeng (Committee member) / Barrett, The Honors College (Contributor) / Chemical Engineering Program (Contributor)
Created2014-05
Description
In this Honors thesis, direct flame solid oxide fuel cells (DFFC) were considered for their feasibility in providing a means of power generation for remote powering needs. Also considered for combined heat and fuel cell power cogeneration are thermoelectric cells (TEC). Among the major factors tested in this project for all cells were life time, thermal cycle/time based performance, and failure modes for cells. Two types of DFFC, anode and electrolyte supported, were used with two different fuel feed streams of propane/isobutene and ethanol. Several test configurations consisting of single cells, as well as stacked systems were tested to show how cell performed and degraded over time. All tests were run using a Biologic VMP3 potentiostat connected to a cell placed within the flame of a modified burner MSR® Wisperlite Universal stove. The maximum current and power output seen by any electrolyte supported DFFCs tested was 47.7 mA/cm2 and 9.6 mW/cm2 respectively, while that generated by anode supported DFFCs was 53.7 mA/cm2 and 9.25 mW/cm2 respectively with both cells operating under propane/isobutene fuel feed streams. All TECs tested dramatically outperformed both constructions of DFFC with a maximum current and power output of 309 mA/cm2 and 80 mW/cm2 respectively. It was also found that electrolyte supported DFFCs appeared to be less susceptible to degradation of the cell microstructure over time but more prone to cracking, while anode supported DFFCs were dramatically less susceptible to cracking but exhibited substantial microstructure degradation and shorter usable lifecycles. TECs tested were found to only be susceptible to overheating, and thus were suggested for use with electrolyte supported DFFCs in remote powering applications.
ContributorsTropsa, Sean Michael (Author) / Torres, Cesar (Thesis director) / Popat, Sudeep (Committee member) / Barrett, The Honors College (Contributor) / Chemical Engineering Program (Contributor)
Created2014-05