Pressure-temperature boundaries for ideal dissociating and ionizing gases

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Virginia Tech


The problem of determining thermodynamic properties of gaseous systems in which real-gas effects must be considered can be greatly simplified through use of existing ideal-gas theories for the processes of dissociation and ionization. Since, however, the ideal dissociating gas theory neglects ionization effects and the ideal ionizing gas theory does not take into account dissociation, an additional assumption must be made in order to use these two theories within a single system experiencing both effects. The added assumption which is made is that the processes of dissociation, single ionization, and higher levels of ionization all occur independently of one another though in a definite order within the system. With this linearizing assumption of independent gas processes the ideal gas theories then can be applied within their respective ranges of application in order to calculate the thermodynamic properties of any system under equilibrium conditions, provided the ranges of application can be determined. Neither the ideal dissociating gas theory nor the ideal ionizing gas theory explicitly defines the pressure-temperature region throughout which the theory is applicable. In the present work an analytic expression is developed which gives the limiting temperature as a function of pressure for the ideal dissociating gas theory. The method is then generalized in the ionization range so as to provide pressure-temperature boundaries for all levels of ionization within the assumption of independent first-level, second-level, and higher-level ionization processes.