Learn: Thermo vocab

Surroundings

Everything outside of the thermodynamic system.

Isolated System

A system across whose boundary neither mass nor energy can cross.

Adiabatic Process

A process in which no heat transfer occurs across the system boundary (Q = 0).

Quasi-Equilibrium Process

A condition in which the state of a system changes slowly enough that it remains in thermodynamic equilibrium at all times.

Gauge Pressure

The difference between absolute pressure and ambient barometric pressure (P_gauge = P_abs - P_atm).

Intensive Property

A property whose value is independent of the total mass of the system.

Extensive Property

A property that is directly proportional to the total mass of the system (e.g., volume V, enthalpy H, total internal energy U).

External Property

A property dependent on an external frame of reference outside the system, such as elevation or velocity.

Enthalpy

A composite thermodynamic property defined as the sum of internal energy and flow energy (h = u + Pv).

Incompressible Substance

A substance whose specific volume (or density) does not change with changing pressure or temperature.

Polytropic Process

A process described analytically by the relationship P*v^n = constant, where n is a constant index.

Saturated State

The state of having just reached 100% liquid or 100% vapor, or existing as a two-phase liquid-vapor mixture.

Triple Point

The unique state where solid, liquid, and vapor phases coexist in thermodynamic equilibrium.

Perfect / Ideal Gas

A gas obeying the ideal gas equation of state (Pv = RT) with constant specific heats.

Quality (Vapor Quality, x)

The ratio of the mass of vapor to the total mass of a saturated liquid-vapor mixture (x = m_vapor / m_total).

Isothermal Process

A thermodynamic process occurring at constant temperature (T = constant).

Heat

Energy transferred across a system boundary solely due to a temperature difference.

Boundary Work (PdV Work)

Work done on or by a fluid during expansion or compression against a boundary (W = ∫ P dV).

Shaft Work

Mechanical work transferred across a boundary via a rotating shaft.

Electrical Work

Energy transfer performed by electrical current moving across a system boundary.

Constant Pressure Specific Heat (Cp)

The amount of energy required to raise the temperature of a unit mass of a substance by one degree at constant pressure.

Compressibility Factor (Z)

The correction factor defined as Z = Pv / (RT), used to quantify deviations from ideal gas behavior.

Reduced Temperature (TR)

The dimensionless ratio of a gas's actual temperature to its critical temperature (TR = T / T_cr).

Reduced Pressure (PR)

The dimensionless ratio of a gas's actual pressure to its critical pressure (PR = P / P_cr).