632 Heat Engines, Entropy, and the Second Law of ThermodynamicsQ22.7Suppose the ambient temperature is 20°C. A gas can be heated to the temperature of the bottom ofthe pond, and allowed to cool as it blows through a turbine. The Carnot efficiency of such an engineis about eTTch===∆8037322%.Q22.8No, because the work done to run the heat pump represents energy transferred into the house byheat.Q22.9A slice of hot pizza cools off. Road friction brings a skidding car to a stop. A cup falls to the floor andshatters. Your cat dies. Any process is irreversible if it looks funny or frightening when shown in avideotape running backwards. The free flight of a projectile is nearly reversible.Q22.10Below the frost line, the winter temperature is much higher than the air or surface temperature. Theearth is a huge reservoir of internal energy, but digging a lot of deep trenches is much moreexpensive than setting a heat-exchanger out on a concrete pad. A heat pump can have a much
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