Use work to move heat from cold to hot; performance measured by COP.
They move heat Q_L from cold to hot using work W. COP_R=Q_L/W; COP_HP=Q_H/W=COP_R+1. Reversible limits: COP_R=T_L/(T_H-T_L). Heat pumps are efficient because they move, not generate, heat; COP typically 3–5.
A heat pump with COP 4 delivers 4 kW of heat for 1 kW electricity.
Refrigerators and heat pumps use work to move heat against the natural direction, so their performance is measured by the coefficient of performance.
Use work to move heat from cold to hot; performance measured by COP.
Refrigerators and heat pumps use work to move heat against the natural direction, so their performance is measured by the coefficient of performance.
The useful heat removed or delivered divided by the work input, and it can exceed one for refrigerators and heat pumps.
A heat pump moves heat from outside into the building, so it can deliver several units of heat for each unit of electrical work.
Typical applications include choosing a heat pump for space heating with a high COP, sizing a refrigeration unit to remove heat from a cold room and comparing the efficiency of a fridge and an air conditioner using their COP.
Study "Heat engines" first (topic 22 of 105 in Thermodynamics & Fluids). It covers the groundwork this topic builds on.
COP can exceed 1. Larger ΔT lowers COP. Air-source and ground-source.
A heat pump with COP 4 delivers 4 kW of heat for 1 kW electricity.
The next topic is "Carnot cycle", which builds directly on this one.
It is classed as Beginner in Thermodynamics & Fluids (topic 23 of 105). It is an entry-level topic. It relies only on basic school mathematics and the ideas introduced earlier in this discipline.
Want to practise? Open the interactive course for quick checks, quizzes, simulations and progress tracking.