pv diagram
The pv diagram is a special form of a phase diagram in which the pressure p of a system is plotted against the specific volume v . If one uses the volume V instead of the specific volume v , one speaks of a pV diagram ; in this case the reference to a constant amount of substance or mass is no longer given and may have to be made as an additional requirement.
The pv diagram is often used to illustrate process flows - with or without phase change - such as the diesel process in the diagram opposite .
According to Gibbs' phase rule , a pure fluid or a fluid mixture with a constant composition has exactly two degrees of freedom . It follows that in the function of the pressure p clearly by the specific volume v and the temperature T will be described.
If you enter this relationship in a three-dimensional diagram , a pVT diagram is created . A PV diagram is obtained by projecting this surface onto the PV plane. The pressure p is the ordinate , the specific volume v is the abscissa and the temperature T is chosen to be constant ( isotherm ) or neglected , depending on the application .
In this diagram, the limits of the aggregate states “solid”, “liquid” and “gaseous” or the individual phases of the fluid are often entered.
literature
- Hans Joachim Eichler , Heinz-Detlef Kronfeldt , Jürgen Sahm: The new basic physics internship. Springer Verlag, Berlin / Heidelberg 2001, ISBN 3-662-21754-6 .
- Jürgen Zeitler, Günter Simon: Physics for Technicians. 7th, updated edition. Fachbuchverlag Leipzig in Carl Hanser Verlag, Munich 2013, ISBN 978-3-446-43377-9 .
See also
Web links
- Changes in the state of the lecture notes (accessed on January 21, 2016)
- State area in the p - v T diagram (accessed on January 21, 2016)