Chemical Engineering @ChemengFiles.Com

Predicting how the future climate of Earth will change as a result of increasing human emissions is one of the greatest problems facing science today. The earth’s climate is the result of a delicate balance between incoming and outgoing radiation. Anthropogenic emissions of aerosol particles into the atmosphere have the potential to affect the earth’s climate in significant ways through both direct and indirect effects on the earth’s radiative balance. One of the largest uncertainties in aerosol radiative forcing is associated with the relationship between atmospheric aerosols and cloud formation, properties, and lifetime. Clouds form by water condensing on small particles (aerosols) in the air (referred to as cloud condensation nuclei, or CCN), and how the increasing levels of atmospheric particles will affect Earth’s clouds and its hydrologic cycle represents one of the key problems in the science of climate. Through theoretical, field, and laboratory investigations, the results presented here reinforce the importance of atmospheric aerosol chemical composition in determining the ability of an aerosol particle to act as a CCN. A study that incorporates surface tension and limited solubility effects, especially of organic compounds, in parameterizations of cloud droplet activation indicate that these chemical effects can rival those of the meteorological environment. An inverse CCN/aerosol closure study of field measurements indicates that assumptions of simple chemistry and mixing state in the interpretation and analysis of field cloud condensation nuclei (CCN) measurements may not necessarily be sufficient and/or realistic, depending heavily on the location of the field study. Properties of organic compounds, such as functional groups, extent of dissociation, and solubility were found to influence the CCN activity of the compounds in laboratory experiments with pure organic aerosols. However, the importance of careful planning of laboratory experiments, in consideration of the properties of the organic compounds, was reinforced and results were carefully interpreted to avoid experimental bias in the conclusions.

The internal energy and the entropy components of the elastic restoring force in rubbers were determined for natural rubber up to an extension ratio of about 3.0. Four different experimental measurements were necessary to determine these components: (1) the force-temperature coefficient at constant temperature and length; (2) the force-pressure coefficient at constant temperature and length; (3) the thermal expansion coefficient at constant length; and (4) the isothermal compressibility at constant length. The force-temperature and the force-pressure coefficients were functions of strain whereas the expansion coefficients and the isothermal compressibilities were independent of strain. These measurements gave an internal energy contribution of 23% for natural rubber independent of the strain over the range of extensions studied.

Zeolite ZSM-5 membranes were prepared on porous [...] disks by in-situ crystallization using a clear solution of optimized composition [...]. During the synthesis, the disk was fixed horizontally at the air-liquid interface and a continuous polycrystalline zeolite film of about 10 µm thickness formed on the bottom surface of disk. Extensive experimentation was carried out to find the optimal composition. Pure gas permeation measurements of the most successful preparation yielded hydrogen:isobutane and n-butane:isobutane ratios of 151 and 18 at room temperature and 54 and 31 at 185°C, respectively.

This dissertation is concerned with the mathematical modelling of oil recovery by steam injection using analytical techniques.

An integral method for generating approximate solutions to the one and two- (three-) dimensional steam injection processes is presented. Due to the qualitatively different character of the problem the one- and two- (three-) dimensional cases are examined separately.

The applicability of the method for the determination of the rate of growth of the steam zone volume in one-dimensional systems is considered. An extensive study of the heat transfer in the surroundings and the hot liquid zone is carried out to complement the one-dimensional implementation of the technique. The resulting class of moving boundary problems and their methods of solution are discussed in detail. The results obtained are then combined with the integral technique to derive upper and lower bounds, asymptotic solutions and approximate solutions to the rate of growth of the steam zone. The important physical parameters are identified and their significance in the design of the process is outlined. In particular, the very important effect of heat transport in the surroundings and the hot liquid zone is fully accounted.

Stress relaxation measurements were made in uniaxial tension under superposed hydrostatic pressures up to 5 kbar at temperatures ranging from -25 to 50[degrees]C. Two lightly filled (Hypalon-40 and Viton-B) and one highly filled elastomer (Neoprene) were studied because their pressure transition lie within the range of the apparatus. The construction and operation of the apparatus are discussed. Measurements on Hypalon and Viton were made either by varying the temperature while maintaining the pressure constant at 1, 1,000, and 2,000 bars, or by holding the temperature constant while varying the pressure from atmospheric to 4,600 bars. The viscoelastic response of Neoprene was measured at 25[degrees]C and pressures up to 4,600 bars.

The measurements were converted to a time dependent shear modulus. Time-temperature and time-pressure superposition was then applied to the reduced data to obtain master curves at 1, 1,000, and 2,000 bars. By introducing either the Murnaghan or the Tait equation of state into the free volume theory, an expression was obtained which describes the shift factors, log a[subscript T,P'] resulting from the empirical shifts into the master curves at atmospheric pressure. This equation then gave an excellent prediction of the empirically found shift factors resulting from forming the master curves at 1,000 and 2,000 bars.

Measurements of the total viscosity and total conductivity were made as a function of position and Reynolds number for the flow of air between two parallel plates with a separation of approximately 0.75 in. The temperature of the upper plate was 103.0[degrees]F and that of the lower plate 70.0[degrees]F. The investigations were carried out at Reynolds numbers from 40,000 to 100,000 and were in good agreement with earlier data obtained at Reynolds numbers up to 40,000. The results obtained indicate little change in the total Prandtl number with increasing Reynolds number from the value of the molecular Prandtl number.

To facilitate ferroelectric-based actuator integration with silicon electronics fabrication technology, we have developed a route to produce biaxially textured ferroelectrics on amorphous layers by using biaxially textured MgO templates.

Using a kinematical electron scattering model, we show that the RHEED pattern from a biaxially textured polycrystalline film can be calculated from an analytic solution to the electron scattering probability. We found that diffraction spot shapes are sensitive to out-of-plane orientation distributions and in-plane RHEED rocking curves are sensitive to the in-plane orientation distribution. Using information from the simulation, a RHEED-based experimental technique was developed for in situ measurement of MgO biaxial texture. The accuracy of this technique was confirmed by comparing RHEED measurements of in-plane and out-of-plane orientation distribution with synchrotron x-ray rocking curve measurements.

Experimental and theoretical studies in the field of fuel gas desulfurization at high temperatures are presented. The performance of different oxides as sorbents for high temperature H2S removal is evaluated. A fixed-bed microreactor was used for this purpose. Basically, streams containing different H2S concentrations were passed through the reactor and the outlet H2S concentration was measured as a function of time. Comparisons between observed and theoretical maximum conversion values are used as a measure of sorbent H2S removal efficiencies.