Problem: A heat engine uses the warm air at the ground as the hotreservoir and t

Question

Problem: A heat engine uses the warm air at the ground as the hotreservoir and the cooler air at an altitude of several thousandmeters as the cold reservoir. If the warm air is at 37 deg.C, and the cold air is at 25 deg. C, what is the maximum possibleefficiency for the engine?
the solution says : Th = 25+273.15= 298.15 K    Tc= 37 + 273.15 = 310 K
my question is: since the warm air is the hot reservoirand the cold air is the cold reservoir, shouldn't Th = 310.15 K andTc = 298.15 K?? A heat engine uses the warm air at the ground as the hotreservoir and the cooler air at an altitude of several thousandmeters as the cold reservoir. If the warm air is at 37 deg.C, and the cold air is at 25 deg. C, what is the maximum possibleefficiency for the engine?
the solution says : Th = 25+273.15= 298.15 K    Tc= 37 + 273.15 = 310 K
my question is: since the warm air is the hot reservoirand the cold air is the cold reservoir, shouldn't Th = 310.15 K andTc = 298.15 K??
the solution says : Th = 25+273.15= 298.15 K    Tc= 37 + 273.15 = 310 K
my question is: since the warm air is the hot reservoirand the cold air is the cold reservoir, shouldn't Th = 310.15 K andTc = 298.15 K??

Explanation / Answer

.    Efficiency is : = 1 - (TC  / TH  )    . We have : 0oC = 273.15 K . Given : Temperature of the hot reservoir is : TH   = 37oC + 273.15 = 310.15 K .       Temperature of the cold reservoir is : TC   = 25oC + 273.15 = 298.15 K . Hence Efficiency is : = 1 - (298.15  / 310.15  ) = 0.0386 = 0.039 . Hope this helps u!

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