SUMMARY The goal of Chapter 19 has been to study the physical principles that govern the operation of heat engines and refrigerators. General Principles Heat Engines Devices that transform heat into work. They require two energy reservoirs at different temperatures. Thermal efficiency Second-law limit: h# 1 2 T C T H h5 W out Q H 5 what you get what you pay Refrigerators Devices that use work to transfer heat from a colder object to a hotter object. Coefficient of performance Second-law limit: K # T C T H 2 T C K 5 Q C W in 5 what you get what you pay Important Concepts A perfectly reversible engine (a Carnot engine ) can be operated as either a heat engine or a refrigerator between the same two energy reservoirs by reversing the cycle and with no other changes. •A Carnot heat engine has the maximum possible thermal efficiency of any heat engine operating between and •A Carnot refrigerator has the maximum possible coefficient of performance of any refrigerator operating between
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