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1. Heat Engines, Heat Pumps, and Refrigerators Getting something useful from heat

5. Power Plant Arrangement Heat flows from T h to T c , turning turbine along the way

10. How much work can be extracted from heat? Hot source of energy Cold sink of energy heat energy delivered from source heat energy delivered to sink externally delivered work: conservation of energy Q T h  Q h  Q c  W =  Q h –  Q c T c efficiency = =  W work done  Q h heat supplied

11. Let’s crank up the efficiency Let’s extract a lot of work, and deliver very little heat to the sink In fact, let’s demand 100% efficiency by sending no heat to the sink: all converted to useful work T h  Q h  Q c  W =  Q h –  Q c T c efficiency = =  W work done  Q h heat supplied

15. Example efficiencies of power plants Power plants these days (almost all of which are heat-engines) typically get no better than 33% overall efficiency

17. Overall efficiency greatly enhanced by cogeneration

18. Heat Pumps Heat Pumps provide a means to very efficiently move heat around, and work both in the winter and the summer

19. Heat Pump Diagram

20. Heat Pumps and Refrigerators: Thermodynamics  W =  Q h –  Q c Hot entity (indoor air) Cold entity (outside air or refrigerator) heat energy delivered heat energy extracted delivered work: conservation of energy Just a heat engine run backwards… T h  Q h  Q c T c efficiency = =  W work done  Q h heat delivered (heat pump) efficiency = =  W work done  Q c heat extracted (refrigerator)

23. Example Labels (U.S. & Canada)