Proposing a math model and using enthalpy method to solve the temperature and flow field distribution around the bubble. Find the influence for different coefficients.

Excess enthalpy combustion utilizes heat recirculation, in which heat is transferred from hot products to cold reactants to effectively preheat the reactants, in order to achieve improved combustion performance through the extension of flammability limits and increased burning rate. This research examines the effect of key parameters in excess enthalpy combustion on combustion stability, fuel conversion, and product species production through experimental and numerical investigation. Operating condition parameters that are studied include inlet reactant equivalence ratio and inlet velocity, and reactor geometry parameters that are studied include reactor channel height and length. Premixed reactants, including gaseous and liquid fuels, are investigated at rich and lean conditions. The examination of liquid fuels and the ability of a reactor to support rich and lean combustion of both gaseous and liquid fuels is a significant demonstration of a reactor’s flexibility for practical applications. This research experimentally and numerically examines excess enthalpy combustion in a counter-flow reactor. First, the counter-flow reactor, previously used for thermal partial oxidation of gaseous hydrocarbon fuels, is used in experiments to reform a liquid hydrocarbon fuel, heptane, to syngas. The effect of inlet operating conditions, including reactant equivalence ratio and inlet velocity, on combustion stability and product composition is explored. Second, lean combustion is demonstrated through experiments in the same counter-flow reactor previously used in reforming studies. The effect of inlet operating conditions, including reactant equivalence ratio and inlet velocity, on combustion stability and pollutant concentrations in combustion products is studied. An analytical model, previously developed for rich combustion, is adapted to qualitatively predict the behavior of the counter-flow reactor in response to changes in lean operating conditions. Third, lean combustion in the counter-flow reactor is further studied by examining the combustion of increasingly complex gaseous and liquid fuels. Again, the effect of inlet operating conditions, including reactant equivalence ratio and inlet velocity, on combustion stability and pollutant concentrations in combustion products is studied. Fourth and finally, a computational scaling study examines the impact of counter-flow reactor channel geometry on combustion stability, temperature increase above adiabatic values, heat recirculation, and fuel and product species conversion efficiency. / text

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Predictive methods have been employed to characterize chemical separation mediums including solvents and absorbents. These studies included creating Abraham solvation parameter models for room-temperature ionic liquids (RTILs) utilizing novel ion-specific and group contribution methodologies, polydimethyl siloxane (PDMS) utilizing standard methodology, and the micelles cetyltrimethylammonium bromide (CTAB) and sodium dodecylsulfate (SDS) utilizing a combined experimental setup methodology with indicator variables. These predictive models allows for the characterization of both standard and new chemicals for use in chemical separations including gas chromatography (GC), solid phase microextraction (SPME), and micellar electrokinetic chromatography (MEKC). Gas-to-RTIL and water-to-RTIL predictive models were created with a standard deviation of 0.112 and 0.139 log units, respectively, for the ion-specific model and with a standard deviation of 0.155 and 0.177 log units, respectively, for the group contribution fragment method. Enthalpy of solvation for solutes dissolved into ionic liquids predictive models were created with ion-specific coefficients to within standard deviations of 1.7 kJ/mol. These models allow for the characterization of studied ionic liquids as well as prediction of solute-solvent properties of previously unstudied ionic liquids. Predictive models were created for the logarithm of solute's gas-to-fiber sorption and water-to-fiber sorption coefficient for polydimethyl siloxane for wet and dry conditions. These models were created to standard deviations of 0.198 and 0.122 logunits for gas-to-PDMS wet and dry, respectively, as well as 0.164 and 0.134 log units for water-to-PDMS wet and dry, respectively. These models are particularly useful in solid phase microextraction separations. Micelles were studied to create predictive models of the measured micelle-water partition coefficient as well as models of measured MEKC chromatographic retention factors for CTAB and SDS. The resultant predictive models were created with standard deviations of 0.190 log units for the logarithm of the mole fraction concentration of water-to-CTAB, 0.171 log units for the combined logarithms of both the mole fraction concentration of water-to-CTAB and measured MEKC chromatographic retention factors for CTAB, and 0.153 log units for the combined logarithms of both the mole fraction concentration of water-to-SDS and measured MEKC chromatographic retention factors for SDS.

Desiccant-enhanced air conditioning equipment has exhibited both the capability to improve humidity control and the potential to save energy costs by lowering the latent energy requirement of the supply air stream. The resulting increasing popularity of desiccant-enhanced air conditioning systems has sparked new interest in the search for a better, more efficient desiccant material. The ultimate goal of this research was to develop a material that, when applied to an existing air-to-air heat exchanger, would achieve the necessary heat and mass transfer in a single process, thus transforming a sensible heat exchanger into a total enthalpy exchanger. This study focuses on the development and determination of appropriate polymeric desiccant materials for use in different heat and mass transfer applications. Various candidate materials were initially studied. It was decided that polyvinyl alcohol best met the pre-determined selection criteria. After the focus material was chosen, numerical models representing two heat and mass transfer applications were created. One-dimensional numerical models were developed for the performance studies of a rotary wheel total enthalpy exchanger. A two-dimensional numerical model was developed for the performance studies of a fixed plate total enthalpy exchanger as well. Material characterization tests were performed to collect material property information required by the numerical models. Sensible, latent, and total efficiencies gathered from both the rotary wheel total enthalpy exchanger and the fixed plate total enthalpy exchanger models indicate potential uses for some candidate polyvinyl alcohol materials. / Master of Science

Abstract not available

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Not available / text

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / The electronic structure, band structure and optical properties of compounds GaAs(1−x)Mx (M = Fe,Cu), for x=0.25, 0.75, and 1 are discussed via Full-potential linearized augmented plane wave calculations. An increase in absorption in the visible spectrum is observed for all compounds, which, however, is associated with an increasingly metallic character as the metal concentration increases, to the point that compound GaFe is an indirect degenerate semiconductor. The addition of Fe and Cu to the compound decreases its stability, as demonstrated by the formation enthalpies, which become progressively more positive as the content in As is decreased. The calculations were performed using both the PBE and PBEsol exchange correlation potentials and the TB-mBJ method was used to verify the band structure obtained. / Consejo Nacional de Ciencia, Tecnología e Innovación Tecnológica / Revisón por pares

Just twenty years have passed since the first papers were published on the application of chemical thermodynamics to the soil-water system (11, 14). Since then, soil physicists have used thermodynamics in an attempt to characterize and l earn more about this intricate system.