### Universal Gas Law

### The First Law

Always true:

For cycles:

For constant volume (no work done):

### Work Done

Always true:

True for constant :

True for constant :

(PV is constant)

True when adiabatic & reversible:

(Isentropic)

Shaft Work

### Constant Pressure

### Constant Volume

### Perfect, Adiabatic & Reversible (Isentropic)

is constant:

is constant:

is constant:

### Enthalpy

### Perfect Gases & Temperature

Change in energy, :

Change in enthalpy, :

Perfect gas constant, :

Perfect gas ratio, :

### Steady Flow Energy Equation (SFEE)

Mass flow rate, :

Volume flow rate, :

- is the density
- is the speed
- is the cross-sectional area of the duct
- is the specific volume

### Wet Vapour

Dryness fraction, :

Wet Property, :

### Clausius’ Inequality

For a **reversible **cycle or process:

For an **irreversible** cycle of process:

### Combining 1st & 2nd Laws

These equations are valid for both reversible and irreversible processes, as all quantities are properties.

### Perfect Gas Processes

Again, these are applicable to both reversible and irreversible processes **so long as the gases are perfect.**

### Efficiencies

General efficiency, :

Thermodynamic Efficiencies, :

Thermal (reversible) efficiency, :

### Isentropic Efficiencies,

Turbine/Engine

Compressor/Pump