thermodynamics glossary

Basics

Thermal equilibrium

a system is in thermal equilibrium if there are no temperature gradients within it. A system is in thermal equilibrium with its surroundings if $ T_{sys} = T_{surroundings} $.

Process

A sequence of equilibrium states which connects two states.

Heat engines

Ideal cycle:

A cycle consists of processes. In an ideal cycle, every process in the cycle is reversible.

Turbine

drops a fluid’s pressure and converts it to rotational mechanical energy

Rankine Cycle

Subcritical Rankine cycle:

The working fluid has $p<p_c$ and $T < T_c$ meaning it is a 2-phase mixture.

Deaerator

A device which removes gases from liquid water after it comes out of the condenser.

Chapter 6

thermal efficiency (of a heat engine): The work output divided by the heat input.

Second Law: Clausius Statement

No heat engine has a thermal efficiency of 100%

Second Law: Kelvin-Planck Statement:

You cannot construct a machine whose only effect is to take heat from a low temperature reservoir to a high-temperature reservoir.

Reversible process:

a reversible process is one which can be reversed without leaving any trace on its surroundings. They are useful to analyze because reversible processes are quasi-static (a system goes through a series of equilibrium states in a reversible process)

Second Law

For an isolated system, $ d S >= 0 $

== Chapter 7

Exergy

the maximum useful work that could be obtained from a system at a given state.

Exergy destruction

Wasted work potential during a process as a result of irreversibilities

Dead state

a system is in a dead state if it is in thermodynamic equilibrium with its environment. A system has zero exergy in a dead state.

Unavailable energy

the portion of energy that cannot be converted to work by even a reversible heat engine.