Chemical Engineering Commons^™

Impact Of Alternative Refrigerants On Evaporator Design And Analysis Of Compact Heat Exchangers, Dadeech Parag

Masters Theses and Doctoral Dissertations

This thesis deals with the evaluation of the impact of alternate refrigerants on the thermal design parameters of different heat exchangers, such as, plate fin and tube, shell and tube evaporator and compact heat exchangers. A computer code has been developed in Quick-Basic language to conduct this investigation.

60. Teiji Tsuruta, Otto Vogl

Emeritus Faculty Author Gallery

No abstract provided.

60. Teiji Tsuruta, Otto Vogl

Otto Vogl

No abstract provided.

A New Spray Evaporation Model Based On Droplet Interface Phenomena, Nihad E. Daidzic, Gangolf Kohnen, Martin Sommerfeld

Aviation Department Publications

In this work the influence of droplet shape oscillations on droplet evaporation is shown. Through nonlinear mode interactions, turbulence and aerodynamic triggering of vibrations cause by vortex shedding, droplets always oscillates in spray flows. Droplet shape oscillation cause higher evaporation rates through several physical phenomena such as an average increase of the superficial surface area, periodic micro-convection and boundary layer destruction, and local saturation pressure changes due to local curvature effects. The inviscid theory of small-amplitude droplet oscillations was used which resulted in better agreement with the measurement data of droplet size distributions in sprays for different axial coordinates.

61. Marian Kryszewski, Otto Vogl

Emeritus Faculty Author Gallery

No abstract provided.

61. Marian Kryszewski, Otto Vogl

Otto Vogl

No abstract provided.

Excess Heat Capacity Surfaces For Water-Alkanol Mixtures By The Uniquac Model, Yaşar Demirel, Halime Ö. Paksoy

Papers in Physical Chemistry

Hydroorganic mixtures are industrial solvents that can serve as media to solubilize either water in hydrocarbon or a hydrophobic substance in water. In many cases the solubilizing capability is obtained via a homogeneous complex aqueous mixtures containing an alcohol. Since excess heat capacity C_P^E, is very sensitive to structural changes in mixtures, concentration and temperature dependence of C_P^E have been calculated by using the UNIQUAC model for the mixtures methanol(l)-water(%, ethanol(l)-water(2), and l-propanol(l)-water(2). The temperature-dependent parameters of the model estimated directly from C_P^E data at more than one different isotherm are used in …

Reaction Fronts In A Porous Medium. Approximation Techniques Versus Numerical Solution, Fernando Escobedo, Hendrik J. Viljoen

Papers in Reaction Kinetics

The flame sheet approximation (FS) and a novel polynomial approximation technique (PA) are compared in terms of their capability to describe reaction fronts of highly exothermic reactions in a porous medium. A one-phase model and a two-phase model of a system with adiabatic walls and a radiant output (to approximate the case of a porous radiant burner) are included in the analysis. By matching the reaction zone solution found by either the FS or PA method with the solutions of the nonreacting zones, the temperature, conversion, and position of the reaction zone were determined. Numerical solutions for catalytic and noncatalytic …

The Study Of The Growth Processes Of The Oxides On Lead Electrodes In Sulfuric Acid Solution, Hesheng Zhai, Xuguang Chen, Jinkua You, Yong Yang, Zugeng Lin

Journal of Electrochemistry

The growth processes of PbO and PbO_2 on lead electrodes have been investigatedby using in-situ methods that are combined with temporary AC resistance measurment technique andin-situ laser scanning photoelectrochemical microscopy.It is found that a linear relationship existsbetween the electrode resistance(R)and￣(1/2) after the electrode is oxidized at +0.6 V(vs.Hg/H_2SO_4/35%H_2SO_4)for more than 5 min.This result suggests that the growth of PbO is well distributedduring the early stage of oxidation.The study by using laser scanning photoelectrochemical microscopyhas further proved this point.The results also show that the growth of PbO_2 takes place and develops.

A Photoelectrochemical Investigation Of Zirconium Oxide Film, Maizhi Yang

Journal of Electrochemistry

A photoelectrochemical investigation has been carried out on zirconium initialoxide film and its oxide film grownanodically at constant rate up to different thickness. Both anodicand cathedic photocurrents on the photocurrent spectrum depended on the potential,but had littlerelation with the forming anedic films or measuring solutions. Photocurrent spectrum and photocurrenttransients suggested that the oxide films on zirconium were duplex layers structure. The internal layerwas ZrO_2 and the external layer ZrO_2·(H_2O)_n. The photocurrent included photogenerated carrier ininternal and external oxide films,as well as internal photoinjection process for electrons from thesubstrate metal into the electrode/electolyte interface reacting with the redox couple. The analysis …

Electroreduction Of Holmium Ion On Iron Electrde In Molten Cholorides, Qiqin Yang, Guankun Liu, Yuzhi Su

Journal of Electrochemistry

The cyclic voltammetry,open circuit potential-time curve after poteritiostaticelectrolysis,current-time curve at potential step,x-ray diffraction and electron probe microanalysiswere used to investigate the electrode process of Ho(Ⅲ)reduced on iron electrode in molten chloridesand the phases of surface alloy layer.The Ho-Fe alloys are formed at first,and then the metallicholmium is deposited when Ho(Ⅲ)is reduced on iron electrede. The charge transfer is reversible. Thefree energies of formation for the four intermetallic compounds of Ho-Fe system,the diffusioncoefficients and diffusion activation energy of Ho in alloyed cathode are determined.

Synthesis Of Li_Xcoo_2 And Its Behaviour In Rechargeable Lithium Battery, Mingfeng Guo, Ruimin Yang, Zebo Zhang, Jincao Ye

Journal of Electrochemistry

The Variations of crystal lattice parameters of Li_xCoO_2 during charge anddischarge have been st ud ied by XRD and AAR spectroscopy.It was found that the Li_xCoO_2 crystalvolume expanded during charge and contracted during discharge.The crystal lattice structure wasbroken because of the formation of Co_3O_4 when deeply charge.The variation of lattice parameter C_0value in cycling process was similar to that in charge process.The variation of 006 peak was the mostsensitive in every case.In case of preheating for 20 hours at 700℃ before operating hightemperature,the 006 peak obtained an enhancement obviously.It has had the good rechargeability inmeasurement of the cyclic voltammograms,the CV …

Electroreduction Of The Nittobenzene On Titanium Electrode Implanted With Palladium, Zhongda Wu, Xianjun Zhu, Hongsen Wang

Journal of Electrochemistry

The titanium substrates were bombarded with 1×10￣(17)～5×10￣(17)ions·cm￣(-2) ofpalladium at the room temperature. The surface composition of implanted electrede and concentration-depth profiles of various elements were measured by AES. The electrored uction processes ofnitrobenzene(NB)in 0.1 mol/L NaOH solution at Pd/Ti electrodes have been investigated by cyclicvoltaivimetry.The results show that the palladium implanted titanium electrodes exhibit a high catalyticactivity in the electroreduction of NB. The NB radical anion,which is the product of one-electronelectroreduction of NB,was detected by ESR in-situ in conjunction with electrochemical methods. Aniline was also detected as a product of electroreduction of NB by using UV-spectra in-situ. According to the …

Electrocatalytic Oxidation Of Formaidehyde And Formic Acid On A Pt/Sb_(Ad) Electrode, Hong Li, Lincai Jiang, Xiong Jiang

Journal of Electrochemistry

The electrocatalytic activity for the oxidation of formaldehyde and formic acid ona Sb-modified platinum (Pt/Sb_(ad))was investigated.Results showed that the Pt/Sb_(ad) electrode waselectrocatalytically more active than a Pt electrode in the anodic oxidation of formaldehyde and formicacid.In the case of formaldehyde,an oxidation peak appeared at a potential of ca.0.7V.During theoxidation of formic acid,a 4-fold increase in the 1st peak current was observed.The Sb-modifiedplatinum electrode was found to be most electrocatalytically active at a coverage of 0.75±0.05.Theelectrocatalytic activity of the Pt/Sb_(ad) electrode can be best explained in terms of the geometrical effect,which may lead to the inhibition of the formation of the …

62. David M Solomon, Otto Vogl, Kenneth Ghiggino

Emeritus Faculty Author Gallery

No abstract provided.

62. David M Solomon, Otto Vogl, Kenneth Ghiggino

Otto Vogl

No abstract provided.

Reproducible Technique For Packing Laboratory-Scale Trickle-Bed Reactors With A Mixture Of Catalyst And Fines, Muthanna H. Al-Dahhan, Yuanxin Wu, Milorad P. Duduković

Chemical and Biochemical Engineering Faculty Research & Creative Works

A Reproducible Procedure for Packing Small-Diameter Packed Beds with a Mixture of Fines and Catalyst is Reported. Such Beds Are Essential for Process Catalyst Testing in Trickle-Flow Reactors. Packing Uniformity Along the Bed, Reproducibility of Single-Phase Pressure Drop and Reproducibility of Liquid Holdup and Two-Phase Flow Pressure Drop in Repacked Beds Has Been Demonstrated. © 1995, American Chemical Society. All Rights Reserved.

Experimental And Numerical Determination Of Fluid Velocity Profiles And Turbulence Intensity In Mixing Vessels, Chun-Chiao Chou

Dissertations

In this study, both a laser-Doppler velocimeter (LDV) and a computational fluid dynamic (CFD) software package (FL UENI) were used to experimentally determine and numerically predict the velocity distribution of an unbaffled and a baffled mixing vessel. Two types of impellers were employed, namely a flat blade turbine (FBT) and a pitched blade turbine (PBT). These impellers were studied in a single-impeller or multiple-impeller configuration in the unbaffled and baffled vessels. The flow characteristics in the impeller regions were measured by LDV and used as boundary conditions in the numerical computation. Turbulence effects were numerically simulated using either the k-c …

Combustion Of Methyl Chloride, Monomethyl Amine, And Their Mixtures In A Two Stage Turbulent Flow Reactor, Fuhe Mao

Dissertations

The feasibility of converting fuel-bound chlorine and nitrogen into HCl and N₂ with reduced pollutant emissions of CO, NO, and unburned hydrocarbons was investigated in a two-stage turbulent flow reactor. The study consists of four segments: completion and validation of the experimental facility, experimental and modeling studies of methyl chloride (CH₃Cl) combustion, similar studies on monomethyl amine (CH₃NH₂), and finally studies on simultaneous CH₃Cl and CH₃NH₂ combustion.

Validation of the experimental facility was made by combustion of ethylene (C₂H₄) and air under both fuel-lean …

Volatilization Of Volatile Organic Compounds From Complex Wastewaters, Syed Sikandar Qadry

Theses

A variety of volatile organic solvents used in the pharmaceutical and specialty chemical industries end up in wastewater collection and treatment systems. EPA has classified these VOCs into groups depending on their potential to volatilize from the wastewaters. In making this classification, Henry's Law, which is valid at very low concentrations, has been used to describe the vapor-liquid equilibrium. But, in reality the concentrations observed in the wastewaters are often too high for Henry's Law to be valid and it is inappropriate to assume that equilibrium has been achieved for every compound.

This project evaluates the volatilization rates, both experimental …

63. Ivan Panayotov, Otto Vogl, Christo Tsvetanov

Emeritus Faculty Author Gallery

No abstract provided.

Spinodals In A Polymer-Dispersed Liquid-Crystal, Chungsea Shen, Thein Kyu

College of Polymer Science and Polymer Engineering

Thermodynamic phase equilibria of a polymer dispersed liquid crystal (PDLC) consisting of
monomeric liquid crystals and a polymer have been investigated theoretically and experimentally.
The equilibrium limits of phase separation as well as phase transition of a PDLC system were
calculated by taking into consideration the Flory–Huggins (FH) theory for the free energy of mixing
of isotropic phases in conjunction with the Maier–Saupe ~MS! theory for phase transition of a
nematic liquid crystal. The correspondence between the Landau–de Gennes expansion and the
Maier–Saupe theory was found and the coefficients were evaluated. The calculation based on the
combined FH-MS theory predicted …

63. Ivan Panayotov, Otto Vogl, Christo Tsvetanov

Otto Vogl

No abstract provided.

Numerical Simulations Of The Effect Of Hydrodynamic Interactions On Diffusivities Of Integral Membrane Proteins, Ashok S. Sangani, Travis L. Dodd, Daniel A. Hammer, Donald L. Koch

Ashok S. Sangani

Proteins in a biological membrane can be idealized as disks suspended in a thin viscous sheet surrounded by a fluid of lower viscosity (Saffman 1976). To determine the effect of hydrodynamic interactions on protein diffusivities in non-dilute suspensions, we numerically solve the Stokes equations of motion for a system of disks in a bounded periodic two-dimensional fluid using a multipole expansion technique. We consider both free suspensions, in which all the proteins are mobile, and fixed beds, in which a fraction of the proteins are fixed. For free suspensions, we determine both translational and rotational short-time self-diffusivities and the gradient …

Large Scale Isolation Of Expression Vector Cassette By Magnetic Triple Helix Affinity Capture, Srinivas V. Sonti, Matthew C. Griffor, T. Sano, S. Narayanswami, Arijit Bose, C. R. Cantor, Albert P. Kausch

Chemical Engineering Faculty Publications

No abstract provided.

Catalyst Wetting Efficiency In Trickle-Bed Reactors At High Pressure, Muthanna H. Al-Dahhan, Milorad P. Duduković

Chemical and Biochemical Engineering Faculty Research & Creative Works

Trickle-Bed Reactors Are Widely Used in Industrial High Pressure Operations (Up to 30 MPa). the Knowledge of Catalyst Wetting Efficiency as a Function of Operating Conditions is Needed for Relating Laboratory and Pilot Scale Reactor Data to Large Scale Reactor Operation. the Available Predictions of the Wetting Efficiency Rest on Data Collected at Atmospheric Pressure. in This Study a Phenomenological Analysis Has Been Developed to Relate the Wetting Efficiency with Operating Conditions Such as Reactor Pressure, Gas and Liquid Flow Rate. Experimental Data for the Wetting Efficiency at High Pressure Have Been Obtained Via a Tracer Technique. the Data Support …

Hydrogen-Atom Direct-Entry Mechanism Into Metal Membranes, G. Zheng, Branko N. Popov, Ralph E. White

Faculty Publications

The hydrogen-atom direct-entry mechanism is used to explain why the steady-state hydrogen permeation current density through a metal membrane is directly proportional to the cathodic current density, i_c, and is independent of the membrane thickness when i_c is small.

A Boundary-Layer Model Of A Parallel-Plate Electrochemical Reactor For The Destruction Of Nitrates And Nitrites In Alkaline Waste Solutions, Shailesh Prasad, John W. Weidner, Andrew E. Farell

Faculty Publications

Electrochemical processes appear to be attractive for treating low level nuclear wastes. The development of a simple divided electrochemical-cell model operating in a batch mode, used for the reduction of nitrates and nitrites from nuclear wastes, is presented. This model, based on a boundary-layer approach, is simple and yet encompasses the key features of a previously developed distributed-parameter model that includes diffusion, migration, and convection as the flux components. Because it dramatically reduces computation time, this boundary-layer model is well suited for use in a complex interactive flowsheet model and for optimization studies. The boundary-layer model is used to predict …

A Parallel-Plate Electrochemical Reactor Model For The Destruction Of Nitrate And Nitrite In Alkaline Waste Solutions, D. H. Coleman, Ralph E. White, D. T. Hobbs

Faculty Publications

A parallel-plate electrochemical reactor model with multiple reactions at both electrodes and anolyte and catholyte recirculation tanks was modeled for the electrochemical destruction of nitrate and nitrite species in an alkaline solution. The model can be used to predict electrochemical reaction current efficiencies and outlet concentrations of species from the reactor, given inlet feed conditions and cell operating conditions. Also, predictions are made for off-gas composition and liquid-phase composition in the recirculation tanks. The results of case studies at different applied potentials are shown here. At lower applied potentials, the model predictions show that the destruction process is more energy …

Lntracrystalline Diffusion Of Benzene In Silicalite : Effect Of Structural Heterogeneity, Dhananjai B. Shah, Chang-Jie Guo, David T. Hayhurst

Chemical & Biomedical Engineering Faculty Publications

The sorption kinetics of benzene in silicalite have been measured gravimetrically using large silicalite crystals of sizes 350 µm × 105 µm × 105 µm and 270 µm × 70 µm × 70 µm in the temperature range 283–343 K. Experiments were performed under conditions that ensured isothermal operation with intracrystalline diffusion control. An analytical expression for the Darken's correction factor (δ In P/δ In a) was derived based on the Hill–de-Boer equation and was used to determine the variation of corrected diffusivity with concentration. The transport diffusivity varied significantly with the adsorbed-phase concentration but the …