coeffcient of performance

COP measures the performance of machines like refrigerators, in an opposite fashion than steam engines.

$\mathrm{COP}=\frac{Q_L}{W}=\frac{Q_L}{Q_H-Q_L}$ $\mathrm{CO}{\mathrm{P}}_{\mathrm{ideal}}=\frac{T_L}{W}=\frac{T_L}{T_H-T_L}$