Efficiency of Real Heat Engines

Early in the development of the steam engine, it was realized that if actual water steam is superheated as a gas well above the boiling point of water to say 800°K and regular liquid is used as a coolant, the engine could be operated between about 800°K and 373°K to improve the efficiency to roughly 

This is actually very good for a heat engine or any engine for that matter. Compare that to an internal combustion engine at the extreme operating temperatures. Thus, if we assume ideal conditions of about 2300°K for combustion of gasoline and a maximum temperature of the exhaust manifold and 

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