Thermal efficiency
The thermal efficiency is a measure of the energy that can be converted to work as a fraction of the total energy.The concept can be expressed mathematically in an equation for calculating efficiency.
\[ \small \eta = \left ( \frac{T_{H}-T_{L}}{T_{H}} \right ) \]
where TL is the temperature of the cold 'sink' and
TH is the temperature of the heat reservoir.
Using this equation the numerical value of efficiency will be a fraction having a value between 0 and 1. Often it is more convenient or easier to express efficiency as a percentage rather than as a fraction. This is done readily by using the comparable formula.
\[\eta \: \: \% = 100\left ( \frac{T_{H}-T_{L}}{T_{H}} \right ) \]
