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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Improving Understanding of Liquid Viscosity Through Experiments and Prediction

Passey, Jeremy W. 05 April 2021 (has links)
Liquid viscosity is an important thermophysical property in process design. While liquid viscosity has been studied for over a century, much has been left unexplored. The behavior of liquid viscosity between the melting point and normal boiling point are well established, but yet there is a lack of experimental data – with only 52% of the compounds in the 801 DIPPR database having experimental liquid viscosity data – and inadequate prediction methods. This project was able to measure liquid viscosity for 30 organic compounds to help fill in the gap in the 801 DIPPR database. The measured results also helped reiterate the need to examine family trends when looking at thermophysical properties. Prediction method shortcomings are briefly discussed when evaluating measured liquid viscosity data. A QSPR model developed by Gharagheizi is tested using liquid viscosity data from the 801 DIPPR database and found to be nonreplicable. A new QSPR model for predicting liquid viscosity at 298.15 K based on chemical family is developed and proven to be a promising starting point for future work.
2

Autoignition Temperatures of Pure Compounds: Data Evaluation, Experimental Determination, and Improved Prediction

Redd, Mark Edward 09 June 2022 (has links)
The Design Institute for Physical Properties (DIPPR) maintains the DIPPR 801 database for the American Institute of Chemical Engineers. Autoignition temperature (AIT) is one of the properties included in the database and is the focus of this work including improvement of the overall state of AIT in the database. Phenomena related to AIT as well as the relevant literature are reviewed. Likewise, the database is presented to respond to significant misuse of the DIPPR 801 database in the literature. The database is evaluated, respecting AIT, as a whole to show where improvement is needed. An experimental study of minimum autoignition temperatures reveals unexpected behavior of pure n-alkanes not predicted by current current phenomenological understanding of autoignition processes. Measurements show an increase at C16 and a dramatic and previously unexplained step increase between C25 and C26. Experimental modifications are presented to compensate the effect of altitude. Measured values for several n-alkanes are reported and compared to the literature. Other ignition experiments and decomposition measurements using differential scanning calorimetry are also reported and examined to elucidate the unexpected trends. Explanations for these trends are proposed. Finally, the implications of this for trends in other chemical families are discussed. A comprehensive examination of AIT family trends reveals variation from the n-alkane family trend. Measured AIT values are presented and discussed. Evaluated AIT values are recommended for several single-group chemical families. Phenomenological explanations for observed differences are proposed and discussed along with the broader implications for these trends. Methods for predicting autoignition temperatures (AIT) have been historically inaccurate and are rarely based on the underlying physical phenomena leading to observed AIT. An improved method for predicting AIT based on the method by the late Dr. William H. Seaton is presented and discussed. The method of Seaton is described in detail. An evaluated data set is used to regress new parameters for the Seaton method parameters. Improvements to Seaton's model and underlying principles are presented and discussed. Finally, an improved AIT prediction method is presented and recommended.
3

Flammability Limits, Flash Points, and Their Consanguinity: Critical Analysis, Experimental Exploration, and Prediction

Rowley, Jeffrey R. 25 June 2010 (has links) (PDF)
Accurate flash point and flammability limit data are needed to design safe chemical processes. Unfortunately, improper data storage and reporting policies that disregard the temperature dependence of the flammability limit and the fundamental relationship between the flash point and the lower flammability limit have resulted in compilations filled with erroneous values. To establish a database of consistent flammability data, critical analysis of reported data, experimental investigation of the temperature dependence of the lower flammability limit, and theoretical and empirical exploration of the relationship between flash points and temperature limits are undertaken. Lower flammability limit measurements in a 12-L ASHRAE style apparatus were performed at temperatures between 300 K and 500 K. Analysis of these measurements showed that the adiabatic flame temperature at the lower flammability limit is not constant as previously thought, rather decreases with increasing temperature. Consequently the well-known modified Burgess-Wheeler law underestimates the effect of initial temperature on the lower flammability limit. Flash point and lower temperature limit measurements indicate that the flash point is greater than the lower temperature limit, the difference increasing with increasing lower temperature limit. Flash point values determined in a Pensky-Martens apparatus typically exceed values determined using a small-scale apparatus above 350 K. Data stored in the DIPPR® 801 database and more than 3600 points found in the literature were critically reviewed and the most probable value recommended, creating a database of consistent flammability data. This dataset was then used to develop a method of estimating the lower flammability limit, including dependence on initial temperature, and the upper flammability limit. Three methods of estimating the flash point, with one based entirely on structural contributions, were also developed. The proposed lower flammability limit and flash point methods appear to predict close to, if not within, experimental error.
4

Aqueous Henry's Law Constants, Infinite Dilution Activity Coefficients, and Water Solubility: Critically Evaluated Database, Experimental Analysis, and Prediction Methods

Brockbank, Sarah Ann 05 July 2013 (has links) (PDF)
A database containing Henry's law constants, infinite dilution activity coefficients and solubility data of industrially important chemicals in aqueous systems has been compiled. These properties are important in predicting the fate and transport of chemicals in the environment. The structure of this database is compatible with the existing DIPPR® 801 database and DIADEM interface, and the compounds included are a subset of the compounds found in the DIPPR® 801 database. Thermodynamic relationships, chemical family trends, and predicted values were carefully considered when designating recommended values. Henry's law constants and infinite dilution activity coefficients were measured for toluene, 1-butanol, anisole, 1,2-difluorobenzene, 4-bromotoluene, 1,2,3-trichlorobenzene, and 2,4-dichlorotoluene in water using the inert gas stripping method at ambient pressure (approximately 12.5 psia) and at temperatures between 8°C and 50°C. Fugacity ratios, required to determine infinite dilution activity coefficients for the solid solutes, were calculated from literature values for the heat of fusion and the liquid and solid heat capacities. Chemicals were chosen based on missing or conflicting data from the literature. A first-order temperature-dependent group contribution method was developed to predict Henry's law constants of hydrocarbons, alcohols, ketones, and formats where none of the functional groups are attached directly to a benzene ring. Efforts to expand this method to include ester and ether groups were unsuccessful. Second-order groups were developed at a reference condition of 298.15 K and 100 kPa. A second-order temperature-dependent group contribution method was then developed for hydrocarbons, ketones, esters, ethers, and alcohols. These methods were compared to existing literature prediction methods.

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