The conversation between human and AI assistant.
What are the difference between heat pump, heat engine and refrigerator?
That's helpful. How efficient are these devices in terms of energy use?
Heat pumps are generally very efficient, with some models boasting a coefficient of performance (COP) of up to 5. In comparison, the most efficient heat engines have a theoretical efficiency limit of around 60%. Refrigerators are less efficient than heat pumps due to the work needed to pump heat in the opposite direction.