Power Plant Engineering - Day 1: Thermodynamics

Vocabulary practice flashcards covering fundamental thermodynamics, properties of working substances, gas laws, and energy equations.

Thermodynamics

The study of heat and work.

Pure Substance

A working substance whose chemical composition remains the same even if there is a change in phase (most commonly water).

Ideal Gas

A working substance which remains in gaseous state during its operating cycle and whose equation of state is $PV = mRT$ (most commonly air).

Pressure

In general, the ratio of force per unit area.

Gage Pressure

The pressure reading from the gage pressure instrument which is higher or lower than atmospheric pressure.

Vacuum Pressure

A pressure that is less than atmospheric pressure.

Absolute Pressure ($P_{\text{abs}}$)

The total pressure measured above absolute zero, calculated as $P_{\text{abs}} = P_g + P_{\text{atm}}$.

Hydrostatic Pressure ($P$)

Pressure exerted by a fluid at rest, calculated as $P = w h$, where $w$ is fluid density and $h$ is fluid height.

Temperature

The degree of hotness or coldness of a substance or body.

Thermometer

An instrument used to measure the temperature of a body or a substance.

Pyrometer

An instrument used to measure high temperature gases.

Absolute-Zero Temperature

The lowest possible theoretical temperature, equal to $-273\,^\circ\text{C}$ or $-460\,^\circ\text{F}$.

Density ($w$)

In thermodynamic terms, the mass per unit volume of a substance ($w = \frac{m}{V}$).

Specific Volume ($v$)

The volume per unit of mass in a substance, also known as the reciprocal of density ($v = \frac{V}{m} = \frac{1}{w}$).

Specific Gravity (SG)

The ratio of the density of a substance to the density of a standard (water for liquids and air for gases).

Internal Energy ($U$)

The heat energy due to the movement of molecules within a substance brought about by its temperature.

Flow Work ($W_f$)

The work required to push fluid into or out of a control volume, calculated as $W_f = P(V_2 - V_1)$ in $\text{kJ}$ or $W_f = P(v_2 - v_1)$ in $\text{kJ/kg}$.

Enthalpy ($H$)

The total heat content of a system, equal to internal energy plus flow work ($h = U + Pv$).

Stagnation Enthalpy ($h_s$)

The total enthalpy of a fluid when brought to rest, given by the relation $h_s = h_o + \frac{v_o^2}{2000}$.

Entropy ($s$)

A thermodynamic property representing the unavailability of a system's thermal energy, defined as $s = \frac{Q}{T}$.

Law of Conservation of Mass

Principle stating that total mass is constant, meaning the total mass entering a system equals the total mass leaving.

Potential Energy (PE)

Energy produced due to the change in elevation, expressed as $P = mgh$.

Kinetic Energy (KE)

Energy produced due to the mass and velocity of a body, given by $KE = \frac{1}{2}mv^2$.

Work ($W$)

The product of the displacement of the body and the component of the force in the direction of the displacement (positive when done by the system, negative when done on the system).

Heat ($Q$)

Energy transferred due to a temperature difference, given by $Q = mc_p(t_2 - t_1)$ (positive when added, negative when rejected).

Zeroth Law of Thermodynamics

States that when two bodies are in thermal equilibrium with a third body, they are in thermal equilibrium with each other and are at the same temperature.

First Law of Thermodynamics

States that one form of energy may be converted into another form, meaning all energy entering a system equals all energy leaving.

Kelvin-Planck Statement

Second law statement declaring it impossible to construct a heat engine that operates in a cycle, receives heat from a high-temperature reservoir, and performs an equivalent amount of work.

Third Law of Thermodynamics

States that the absolute entropy of a pure crystalline substance in complete internal equilibrium is zero at zero degrees absolute.

Boyle's Law

An ideal gas law describing an isothermal process ($T = C$) where the pressure-volume product is constant: $P_1 V_1 = P_2 V_2$.

Charles's Law

An ideal gas law governing isobaric ($\frac{V_1}{T_1} = \frac{V_2}{T_2}$) and isochoric ($\frac{P_1}{T_1} = \frac{P_2}{T_2}$) processes.

Specific Heat Ratio ($k$)

The ratio of constant pressure specific heat to constant volume specific heat ($k = \frac{c_p}{c_v}$), equal to $1.4$ for cold air and $1.3$ for hot air.