• id: JTHERM-01-N12
• title: Refrigerators and Coefficient of Performance
• tags: refrigerator, COP, heat-pump

A refrigerator is a heat engine run backwards: it absorbs $Q_C$ from the cold reservoir and rejects $Q_H = Q_C + W$ to the hot reservoir, using work W. COP = $Q_C/W = Q_C/(Q_H - Q_C)$. For Carnot refrigerator: COP = $T_C/(T_H - T_C)$. COP can be greater than 1 (more heat removed than work input). A heat pump heats a room by absorbing heat from cold outdoors: COP_hp = $Q_H/W = T_H/(T_H - T_C)$. Relation: $\text{COP}_{\text{hp}} = \text{COP}_{\text{ref}} + 1$.