Paper 20: The Thermodynamics of Charging and Discharging Processes

Abstract

A comprehensive analysis of charging and discharging processes is presented. The work is of particular relevance to gas exchange processes which occur in internal combustion engines. A rigorous treatment is given of discharge from and charge to a container. In the discharge process irreversibility in the container and the outlet passage are considered separately. A unique pressure-temperature relation is derived for a special case of the charging process and an equation giving the entropy change in the container is derived. It is shown that the mass trapped in the container is a linear function of the pressure in the container. The case of discharge from one container to another is considered, as is the problem of consecutive charging and discharging of one container. For simultaneous charging and discharging no entirely rigorous analysis can be derived. Two analyses—those of ‘filling and emptying’ and ‘perfect displacement’—are presented.