Digital Commons Network^™

Simulated Annealing Technique To Design Minimum Cost Exchanger, Nadeem Muhammed Khalfe, Sandip K. Lahiri, Shiv K. Wadhwa

Nadeem Khalfe

Owing to the wide utilization of heat exchangers in industrial processes, their cost minimization is an important target for both designers and users. Traditional design approaches are based on iterative procedures which gradually change the design and geometric parameters to satisfy a given heat duty and constraints. Although well proven, this kind of approach is time consuming and may not lead to cost effective design as no cost criteria are explicitly accounted for. The present study explores the use of non-traditional optimization technique called simulated annealing (SA), for design optimization of shell and tube heat exchangers from an economic point …

Formation Of Organized Nanostructures From Unstable Bilayers Of Thin Metallic Liquids, Mikhail Khenner, Sagar Yadavali, Ramki Kalyanaraman

Mathematics Faculty Publications

Dewetting of pulsed-laser irradiated, thin (< 20 nm), optically reflective metallic bilayers on an optically transparent substrate with a reflective support layer is studied within the lubrication equations model. A steady-state bilayer film thickness (h) dependent temperature profile is derived based on the mean substrate temperature estimated from the elaborate thermal model of transient heating and melting/freezing. Large thermocapillary forces are observed along the plane of the liquid-liquid and liquid-gas interfaces due to this h-dependent temperature, which, in turn, is strongly influenced by the h-dependent laser light reflection and absorption. Consequently the dewetting is a result of the competition between thermocapillary and intermolecular forces. A linear analysis of the dewetting length scales established that the non-isothermal calculations better predict the experimental results as compared to the isothermal case within the bounding Hamaker coefficients. Subsequently, a computational non-linear dynamics study of the dewetting pathway was performed for Ag/Co and Co/Ag bilayer systems to predict the morphology evolution. We found that the systems evolve towards formation of different morphologies, including core-shell, embedded, or stacked nanostructure morphologies.

Starting Radial Subdiffusion From A Central Point Through A Diverging Medium (A Sphere): Heat-Balance Integral Method, Jordan Hristov

Jordan Hristov

The work presents an integral solution of the time-fractional subdiffusion equation as alternative approach to those employing hypergeometric functions. The integral solution suggests a preliminary defined profile with unknown coefficients and the concept of penetration (boundary layer) well known from the heat diffusion and hydrodynamics. The profile satisfies the boundary conditions imposed at the boundary of the boundary layer that allows its coefficients to be expressed through the boundary layer depth as unique parameter describing the profile. The technique is demonstrated by a solution of a time fractional radial equation concerning anomalous diffusion from a central point source in a …

Formation Of Organized Nanostructures From Unstable Bilayers Of Thin Metallic Liquids, Mikhail Khenner, Sagar Yadavali, Ramki Kalyanaraman

Mikhail Khenner

Dewetting of pulsed-laser irradiated, thin (< 20 nm), optically reflective metallic bilayers on an optically transparent substrate with a reflective support layer is studied within the lubrication equations model. A steady-state bilayer film thickness (h) dependent temperature profile is derived based on the mean substrate temperature estimated from the elaborate thermal model of transient heating and melting/freezing. Large thermocapillary forces are observed along the plane of the liquid-liquid and liquid-gas interfaces due to this h-dependent temperature, which, in turn, is strongly influenced by the h-dependent laser light reflection and absorption. Consequently the dewetting is a result of the competition between thermocapillary and intermolecular forces. A linear analysis of the dewetting length scales established that the non-isothermal calculations better predict the experimental results as compared to the isothermal case within the bounding Hamaker coefficients. Subsequently, a computational non-linear dynamics study of the dewetting pathway was performed for Ag/Co and Co/Ag bilayer systems to predict the morphology evolution. We found that the systems evolve towards formation of different morphologies, including core-shell, embedded, or stacked nanostructure morphologies.

Analysis Of Biomass/Coal Co-Gasification For Integrated Gasification Combined Cycle (Igcc) Systems With Carbon Capture, Henry A. Long Iii

University of New Orleans Theses and Dissertations

In recent years, Integrated Gasification Combined Cycle Technology (IGCC) has become more common in clean coal power operations with carbon capture and sequestration (CCS). Great efforts have been spent on investigating ways to improve the efficiency, reduce costs, and further reduce greenhouse gas emissions. This study focuses on investigating two approaches to achieve these goals. First, replace the subcritical Rankine steam cycle with a supercritical steam cycle. Second, add different amounts of biomass as feedstock to reduce emissions. Finally, implement several types of CCS, including sweet- and sour-shift pre-combustion and post-combustion.

Using the software, Thermoflow®, this study shows that utilizing …

Effects Of Internals Configurations On Heat Transfer And Hydrodynamics In Bubble Columns - With And Without Solid Particles, Anil Kumar Jhawar

Electronic Thesis and Dissertation Repository

Internals of different types are required in a number of industrial applications of bubble columns to achieve the desired mixing or to remove the heat of reaction to maintain desired temperature and isothermal conditions of operation. Some of these applications include Fischer-Tropsch synthesis, methanol synthesis, and production of dimethyl ether (DME). The presence of internals however can alter the column hydrodynamics and mixing patterns which could influence reactor performance. A fast response probe capable of capturing bubble dynamics, as well as detecting flow direction is used to study the effect of internals on local heat transfer and column hydrodynamics in …

Chemical Templating By Afm Tip-Directed Nano-Electrochemical Patterning, Kyle A. Nelson

Theses and Dissertations

This work has examines the creation and use of chemical templates for nanocircuit and other nanodevice fabrication. Chemical templating can be useful in attachment, orientation and wiring of molecularly templated circuits. DNA origami provides a suitable method for creating molecularly templated circuits as DNA can be folded into complex shapes and functionalized with active circuit elements, such as semiconducting nanomaterials. Surface attachment of DNA origami structures can be accomplished by hybridization of dangling single-stranded DNA (ssDNA) on the origami structures with complementary surface-bound strands. Chemical templating provides a pathway for placing the patterned surface-bound attachment points needed for surface alignment …

Modeling Solid Propellant Ignition Events, Daniel A. Smyth

Theses and Dissertations

This dissertation documents the building of computational propellant/ingredient models toward predicting AP/HTPB/Al cookoff events. Two computer codes were used to complete this work; a steady-state code and a transient ignition code Numerous levels of verification resulted in a robust set of codes to which several propellant/ingredient models were applied. To validate the final cookoff predictions, several levels of validation were completed, including the comparison of model predictions to experimental data for: AP steady-state combustion, fine-AP/HTPB steady-state combustion, AP laser ignition, fine-AP/HTPB laser ignition, AP/HTPB/Al ignition, and AP/HTPB/Al cookoff. A previous AP steady-state model was updated, and then a new AP …

Modeling Chemical Degradation And Proton Transport In Perfluorosulfonic Acid Ionomers, Milan Kumar

Doctoral Dissertations

The ionomer-membrane interface in a membrane electrode assembly connects the catalyst and membrane and allows hydrated protons to move between the catalyst and membrane. The continuous operation of the polymer membrane electrolyte fuel cell at high temperature and/or in frequent freeze/thaw cycles leads to membrane degradation and delamination of the interface, which lower the proton conductivity. In this dissertation, we modeled the chemical degradation and proton conductivity of perfluorosulfonic acid (PFSA) ionomers by ab initio calculations and macroscopic modeling. All ab initio calculations were performed using Gaussian 03 suites of program by employing B3LYP/6-311++G** method/basis set. The macroscopic modeling involves …

Process Intensification Routes For Mineral Carbonation, Rafael M. Santos, Tom Van Gerven

Faculty Publications and Scholarship

Mineral carbonation is a realistic route for capture and storage of carbon dioxide. The principal advantages of this approach are the chemical stability and storage safety of mineral carbonates, the opportunities for process integration available, and the potential for conversion of low-value materials into useful products. In this work the valorisation of alkaline waste materials from thermal processes by mineral carbonation utilizing intensified and integrated mineral carbonation routes is explored. Process intensification is the chemical engineering of the 21st century, and aims at providing the paradigm-shifting techniques that will revolutionize the industry. The combination of process intensification and process integration …

Gas-Liquid Slug Formation At A Rectangular Microchannel T-Junction: A Cfd Benchmark Case, Rafael M. Santos, Masahiro Kawaji

Faculty Publications and Scholarship

Computational fluid dynamics (CFD) is an important tool for development of microfluidic systems based on gas-liquid two-phase flow. The formation of Taylor slugs at microchannel T-junctions has been studied both experimentally and numerically, however discrepancies still exist because of difficulties in correctly representing experimental conditions and uncertainties in the physics controlling slug flow, such as contact line and velocity slip. In this paper detailed methods and results are described for the study of Santos and Kawaji [1] on the comparison of experimental results and numerical modeling. The system studied consisted of a rectangular microchannel T-junction nominally 100μm in hydraulic diameter, …

Membrane Biodiesel Production And Refining Technology: A Critical Review, Abdul Aziz Abdul Raman

Abdul Aziz Abdul Raman

Membranes processes for the production and refining of biodiesel are being increasingly reported. Membrane technology has attracted the interest of researchers for its ability to provide high purity and quality biodiesel fuel besides its remarkable biodiesel yields. Membranes have numerous numbers of useful properties such as resistance to mechanical, chemical and thermal stress, high available surface area per unit volume, high selectivity, and ability to control the components contact between the two phases makes them potential. These properties have made them to be potential candidates for both upstream and downstream biodiesel production and refining applications. In this regards, this paper …

Refining Technologies For The Purification Of Crude Biodiesel, Abdul Aziz Abdul Raman

Abdul Aziz Abdul Raman

In biodiesel production, downstream purification is an important step in the overall process. This article is a critical review of the most recent research findings pertaining to biodiesel refining technologies. Both conventional refining technologies and the most recent biodiesel membrane refining technology are reviewed. The results obtained through membrane purification showed some promise in term of biodiesel yield and quality. Also, membranes presented low water consumption and less wastewater discharges. Therefore, exploration and exploitation of membrane technology to purify crude biodiesel is necessary. Furthermore, the success of membrane technology in the purification of crude biodiesel could serve as a boost …

Lectio Praecursoria, Kari Myöhänen

Kari Myöhänen

Lectio praecursoria: Modelling of combustion and sorbent reactions in three-dimensional flow environment of a circulating fluidized bed furnace

Transient Flow Of A Generalized Second Grade Fluid Due To A Constant Surface Shear Stress: An Approximate Integral-Balance Solution, Jordan Hristov

Jordan Hristov

Integral balance solution to start-up problem of a second grade viscoelastic fluid caused by a constant surface stress at the surface has been developed by an entire-domain parabolic profile with an unspecified exponent. The closed form solution explicitly defines two dimensionless similarity variables ξ = y ν t and 2 D0 p t= χ = ν β , responsible for the viscous and the elastic responses of the fluid to the step jump at the boundary. Numerical simulations demonstrating the effect of the various operating parameter and fluid properties on the developed flow filed, as well comparison with the existing …

Modeling And Synthesis Of Functionalized Meta-Poly(Phenylene Ethynylene) Helical Structures, Ha Nguyen

All Dissertations

The ability of meta-poly(phenylene ethynylene) (mPPE) materials to undergo random coil to helix conformational changes under select conditions affords many opportunities for their use in sensor, separation, catalysis, and bio-related applications. Thus, to advance the development of these materials, a modeling procedure based on replica exchange molecular dynamics (REMD) simulation was developed to reliably assess factors affecting the folding behaviors of functionalized mPPE variants in solution. A combinational modeling study of 20 functionalized mPPEs in five solvent conditions provided insight into how mPPE secondary structure is impacted by the complex relationship between mPPE functional groups and solvent moieties. Further, these …

Synthesis And Characterization Of Catalysts For The Selective Transformation Of Biomass-Derived Materials, Isaac Tyrone Ghampson

Electronic Theses and Dissertations

The experimental work in this thesis focuses on generating catalysts for two intermediate processes related to the thermal conversion of lignocellulosic biomass: the synthesis and characterization of mesoporous silica supported cobalt catalysts for the Fischer-Tropsch reaction, and an exploration of the reactivity of bulk and supported molybdenum-based nitride catalysts for the hydrodeoxygenation (HDO) of guaiacol, a lignin model compound. The first section of the work details the synthesis of a series of silicasupported cobalt Fischer-Tropsch catalysts with pore diameters ranging from 2-23 nm. Detailed X-ray diffraction measurements were used to determine the composition and particle diameters of the metal fraction, …

Proteome Based Development Of Novel Affinity Tail For Immobilized Metal Affinity Chromatography And Hydrophobic Interaction Chromatography, Neha Tiwari

Graduate Theses and Dissertations

At industrial scale, reducing the step in purification and recovery is desired; this not only decreases the cost but also increases the yield. Hydrophobic Interaction Chromatography (HIC) and Immobilized Metal Affinity Chromatography (IMAC) both are not harsh on biological structure or activity of proteins; also both the techniques are economical and therefore a suitable choice at industrial level. This dissertation comprises of three parts. Purpose for the Part I was to identify and characterize Escherichia coli proteins which display affinity towards both IMAC and Hydrophobic Interaction Chromatography (HIC). Co (II) IMAC was chosen as the primary capture step, followed by …

Degradation Of Polystyrene Foam Under Radiant Heat Flux, James Butler

Graduate Theses and Dissertations

As the demand for liquefied natural gas has increased, safety concerns about the performance of transport vessels under fire conditions have been raised. Current codes for the sizing of the pressure relief systems require that the vessels are able to withstand an emmissive heat flux of 108kW/m2 and do not take into account the effects of insulation loss due to thermal decomposition of the insulation materials. To address this possible oversight in the current code models were presented to a working group organized by the Society of International Gas Tanker and Terminal Operators Ltd. focusing on the decomposition rate of …

Adsorption And Diffusion Of Light Hydrocarbons In Ddr Zeolite, Adam Vidoni

Electronic Theses and Dissertations

This thesis reports the results of an experimental study aimed at characterizing the transport properties of DDR crystals (a pure silica zeolite analog) by the “zero length column” technique. This material is potentially useful as a size selective molecular sieve adsorbent for separation of CH₄ – CO₂ in the upgrading of low grade natural gas (or biogas) as well as for the separation of C₃H₆ - C₃H₈ for production of polypropylene. In both these applications pure silica zeolites (such as DDR) have important practical advantages over the traditional cationic zeolites since they …

Characterization Of Mesoporous Materials Via Fluorescent Spectroscopic Methods, Raymond Russell Kennard

Electronic Theses and Dissertations

There are three components that need to be understood to create new porous membranes for industrial applications. 1.) To understand appropriate synthesis conditions to create a successful membrane system. 2.) To understand how the microstructures generated in synthesis affect the transport properties of that system. 3) To be able to characterize the heterogeneity of the fabricated membrane’s transport and physical structure.

Presented within this manuscript are new characterization methods to increase the understanding in membrane technology. It will be demonstrated that the novel application of standard fluorescent methods and the development of new fluorescent methods techniques allows for the measurement …

Light-Emitting Nanocomposites And Novel Amorphous Polymers For Optical Applications, Kyle Gipson

All Dissertations

Polymeric optical materials generally are comprised of amorphous polymers that are transparent in at visible wavelengths but exhibit strong absorption bands in the near-infrared making them less useful for many optical applications. Attenuation, which is the absorption per unit length, largely results from the high vibrational energy associated with carbon-hydrogen bonds contained in the polymer backbone. Attenuation can be mitigated by optical amplification utilizing light emitting additives. Investigated in this dissertation are synthesis techniques for the fabrication of light-emitting polymer nanocomposites and their resultant thermal and rheological characteristics for potential use as polymer optical fibers or films.
Inorganic nanocrystals doped …

Chlorine Absorption Utilizing Caustic Sodium Sulfite, Henry Mcdonald

All Theses

A scrubber was required to abate a waste stream containing chlorine gas created in the electrolytic dissolution step of the aqueous polishing process at the Mixed Oxides Fuel Fabrication Facility at Savannah River Site, South Carolina. A method of absorption that utilized caustic sodium sulfite as the scrubbing agent was studied for implementation in the process. This method was found to be highly efficient with respect to process requirements, and it was also found to provide enhanced performance over the more conventional method of chlorine scrubbing which uses only aqueous sodium hydroxide as a reagent. Sulfite provides an additional advantage …

Simulated Annealing Technique To Design Minimum Cost Exchanger, Sandip K. Lahiri

Dr. Sandip Kumar Lahiri

Owing to the wide utilization of heat exchangers in industrial processes, their cost minimization is an important target for both designers and users. Traditional design approaches are based on iterative procedures which gradually change the design and geometric parameters to satisfy a given heat duty and constraints. Although well proven, this kind of approach is time consuming and may not lead to cost effective design as no cost criteria are explicitly accounted for. The present study explores the use of non-traditional optimization technique called simulated annealing (SA), for design optimization of shell and tube heat exchangers from an economic point …

Selective Deposition Of Metallic And Semiconductor Materials Onto Dna Templates For Nanofabrication, Jianfei Liu

Theses and Dissertations

This work examines the selective deposition of metallic and semiconductor materials onto DNA templates for the fabrication of nanodevices. DNA origami provides a simple and robust method for folding DNA into a variety of shapes and patterns and makes it possible to create the complex templates needed for nanodevices, such as nanoelectronic circuits, plasmonics, and nanosensors. Metallization of DNA origami templates is essential for the fabrication of such nanodevices. In addition, selective deposition of semiconductor materials onto the DNA template is of importance for making many nanodevices such as nanocircuits. Metallization of DNA origami presents several challenges beyond those associated …

Indirect Electrochemical Reduction And Cotton Dyeing Process In Fe(Ⅲ)-Oxalate-Calcium Gluconate System, Qing-Zhi Wang, Wei Wang

Journal of Electrochemistry

The electrochemical behavior and possible reaction mechanism in Fe(Ⅲ)-oxalate-calcium gluconate system were studied by cyclic voltammetry. The results showed that Fe(Ⅱ)-gluconate was the final reductant. The reduction time, the working voltage and the cathode area influenced the current efficiency. The high current efficiency of 89% for the indirect electrochemical reduction of Vat Scarlet R could be achieved with reduction time of 10 min, working voltage of 4 V and cathode area of 40 cm2 in Fe(Ⅲ)-oxalate-calcium gluconate system.

Microemulsion Preparation And Electrochemical Characterization Of Pt/C，Ptir/C Electrocatalysts, Ya-Ping Zeng, Sheng Sui

Journal of Electrochemistry

The Pt/C electrocatalysts were prepared by three different systems and the PtIr/C electrocatalysts were prepared with four different Ir contents. The samples were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), cyclic voltammetry (CV), potentiostatic and potentiodynamic polarizations measurements. The experimental results confirmed that the electrocatalyst particles prepared by the microemulsion method were well distributed on XC-72R supports with the active particle sizes of 5～10nm and good electrocatalysts activity. The Pt85Ir15/C electrocatalysts showed the highest overall electrochemical activity in unitized regenerative fuel cell.

Electrochemical Properties Of Tungstogermanate And Electrocatalysis Of H2o2 On Gew11co/P-Opd/Gc Electrode, Li-Li Zhu, Jian-Ying Qu, Jue Wang, Hao-Yue Feng

Journal of Electrochemistry

The electrochemical properties of Co-substituted trimeric tungstogermanate containing Keggin fragments were studied. Cyclic voltammograms revealed two couples of reversible redox peaks on glassy carbon (GC) electrode in acid solutions. They corresponded to two-electron reductions accompanying by the additions of four protons and three protons, respectively, both were controlled by adsorption. The differences in the peak potentials of 2-electron-4-proton and 2-electron-3-proton reactions were 31 mV and 35 mV, respectively..Furthermore, the tungstogermanate (GeW11Co) modified GC electrode with functionalization by poly(o-phenylenediamine) (P-oPD) was prepared readily by electropolymerization. The GeW11Co/P-oPD/GC electrode could electrocatalyze the reduction of hydrogen peroxide, which showed good stability and quick …

Preparation And Characterization Of The Lani0.6fe0.4o3-Δ Cathode For Intermediate Temperature Solid Oxide Fuel Cell, Hang Liu, Bo Huang, Xin-Jian Zhu

Journal of Electrochemistry

The LaNi0.6Fe0.4O3-δ as cathode material for intermediate temperature solid oxide fuel cell was prepared using a combustion synthesis technique. The X-ray diffraction (XRD) pattern showed that the single-phase LaNi0.6Fe0.4O3-δ perovskite could be obtained after heat treatment at 600°C. The TEM and SEM images of the synthesized powders revealed that the grains were 50-100nm. According to the electrochemical impedance spectra (EIS), the polarization resistance of the symmetric cell LaNi0.6Fe0.4O3-δ/ScSZ/LaNi0.6Fe0.4O3-δ sintered at 1050°C was the smallest (0.70Ω?cm2, 0.27Ω?cm2 and 0.12Ω?cm2 at 750°C, 800°C and 850°C, respectively). In the presence of the Fe-Cr alloy interconnection at 750°C, the cathode performance showed that, with …

Dynamic Modeling And Characteristic Analysis Of Proton Exchange Membrane Fuel Cell, Qiu-Hong Jia, Ming Han, Bin Deng, Cai-Zhi Zhang

Journal of Electrochemistry

In this paper, a dynamic model of PEMFC is developed to estimate the dynamic performance of PEMFC by analyzing in detail the influence factors of voltage of PEMFC including various losses. The partial pressure of hydrogen and oxygen is obtained using the differential form of the ideal-gas equation in this model. The steady-state model is obtained by setting reasonable parameter values. The simulation results and experimental results have good consistency, which shows that the simulation model is correct, reasonable and effective. It analyzed the dynamic response characteristics of the output voltage and the partial pressure of hydrogen in condition of …