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Efficiency: Human and Automobile
Efficiency: Human and Automobile

Efficiency: Human and Automobile

In “Why Does Body Temperature Increase During Exercise?” (LiveStrong.com, August 31, 2021), Sara Lindberg writes:

When you use your muscles during exercise, 80 percent of the total energy is converted to heat, while only 20 percent is used for muscle contraction, says board-certified Philadelphia-based primary care doctor Ava Williams, MD. “This heat energy is distributed throughout your body and can cause your body temperature to increase,” she says.


In “Engine Efficiency” they write:

Modern gasoline engines have a maximum thermal efficiency of more than 50%,[1] but road legal cars are only about 20% to 35% when used to power a car. In other words, even when the engine is operating at its point of maximum thermal efficiency, of the total heat energy released by the gasoline consumed, about 65-80% of total power is emitted as heat without being turned into useful work, i.e. turning the crankshaft.[2] Approximately half of this rejected heat is carried away by the exhaust gases, and half passes through the cylinder walls or cylinder head into the engine cooling system, and is passed to the atmosphere via the cooling system radiator.[3] Some of the work generated is also lost as friction, noise, air turbulence, and work used to turn engine equipment and appliances such as water and oil pumps and the electrical generator, leaving only about 20-35% of the energy released by the fuel consumed available to move the vehicle.


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