I stopped taking written notes here… Any examples will still be done in Goodnotes though. See course notes. See the State Postulate.
Process Definition
The change a system undergoes from one equilibrium state to another
They often involve:
- mechanical work
- heat transfer
Example
Like a hot ball undergoing the process of cooling down to its final equilibrium state.
Exhaust cooling down to normal temperature and pressure.
Types of processes
- Isobaric - constant P
- Isothermal - constant T
- Isochoric - constant V
- Adiabatic - no heat in or out of system
Piston with stoppers
A piston with stoppers has two phases…
- Isochoric until the stoppers
- Isobaric after the stoppers
Quasi-equilibrium Process
A system will inherently go through non-equilibrium (intermediate states) during a process.
For example, for a hot ball, the outside of the ball will cool before the inside before reaching its equilibrium state.
Quasi-equilibrium process
If the process is sufficiently slow, such that the system remains infinitesimally close to thermodynamic equilibrium throughout
Basically, if the process within an element itself happens way faster than the overall change to equilibrium.
Things that affect this are thermal mass, and thermal conductivity.
Example
A piston compressing is an example of this, the piston motion is a slow process relative to the air molecule motion (where the molecules gets bunched up at the top and communicates this faster than the piston moves). This, as a quasi-equilibrium process, can be considered a homogenous mixture of air.
Spring piston
An example of a quasi-equilibirum process that is pretty common is a piston with a spring on top
Cycles
Cycle definition
A cycle is a process that is cyclic (i.e, the initial and final states are the same)
The final state is relative then (must be defined).
Cycles often involve:
- heat and work Examples include:
- gas-turbines
- heat pumps