Thermodynamic properties of gases

Type of content
Theses / Dissertations
Publisher's DOI/URI
Thesis discipline
Chemical Engineering
Degree name
Doctor of Philosophy
Publisher
University of Canterbury
Journal Title
Journal ISSN
Volume Title
Language
English
Date
1975
Authors
Couldwell, C.M.
Abstract

In chemical engineering, there is a need to understand p-V-T-x properties of gases for design purposes. These properties have been the subject of study since the classical work of Robert Boyle in 1662. Other major advances over the intervening period have been the results of work by Jacques Charles who proposed (in 1802) a gas law where the pressure remained constant, John Dalton (1801) who gave his name to the law of additivity of partial pressures, Amadeo Avagadro (1811) who postulated that equal volumes of all gases contain equal numbers of molecules under the same conditions of temperature and pressure, and Amagat from whom, in 1880, we have a law of additive volumes. These laws can all by expressed by the equation generally known as the ideal gas law. These laws are valid at low pressures, becoming exact as the limit to real behaviour as density tends to zero.

At higher temperatures and pressures, real gases show significant deviations from perfect behaviour which depend on temperature, pressure and composition. An understanding of real gas behaviour is necessary in a large number of engineering applications since pressures of up to many thousands of bars are not uncommon. Much recent work has been devoted to (a) equations of state suitable for imperfect gases, (b) correlation of properties between different gases, and (c) relations between the properties of mixed gases and those of the pure components.

A new method for experimentally determining second virial coefficients of condensable gases is described. This method avoids the difficult volume calibrations necessary with former techniques and evaluates the second virial coefficient in terms of three pressure measurements. Measurements are reported for n-hexane at temperatures of 328.15 K, 343.15 K, 358.15 K and 373.15 K using this method. These values do not agree with the generally accepted second virial coefficients from the literature and reasons are advanced to explain this.

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