How Efficient is a 100-hp Car Engine Compared to Carnot Efficiency?

[mmg0789]

A 100-hp car engine operates at about 15 percent efficiency. assume that the engine's water temperature is 85deg C is its cold-temperature (exhaust) reservoir and 500deg C is its thermal "intake" temperature (the temperature of the exploding gas/air mixture)

a)calculate its efficiency relative to its maximum possible (Carnot) efficiency

b) estimate how much power (in watts) goes into moving the car, and how much heat, in joules and in kcal, is exhausted to the air in 1 h.

--i'm not sure how to go about this problem any help is appreciated


Thanks in Advance

 

[OlderDan]

A 100-hp car engine operates at about 15 percent efficiency. assume that the engine's water temperature is 85deg C is its cold-temperature (exhaust) reservoir and 500deg C is its thermal "intake" temperature (the temperature of the exploding gas/air mixture)

a)calculate its efficiency relative to its maximum possible (Carnot) efficiency

b) estimate how much power (in watts) goes into moving the car, and how much heat, in joules and in kcal, is exhausted to the air in 1 h.

--i'm not sure how to go about this problem any help is appreciated


Thanks in Advance

The Carnot efficiency is easily calculated. What percent of the maximum possible efficiency (the Carnot efficiency) is the engine achieving?

The 15% efficiency tells you what fraction of the input energy is going into moving the car. The rest goes out in the exhaust.