An ideal engine (Carnot) is rated at 50 % efficiency when it is able to exhaust heat at a temperature of 20 ºC. If the exhaust temperature is lowered to 30 ºC, what is the new efficiency.

Respuesta :

The new efficiency of the ideal engine rated at 50% is : 59%

Given data :

Inital exhaust temperature = 20ºC

Final exhaust temperature = - 30 ºC

The efficiency of an ideal engine can be calculated with the formula below

η = 1 - Texhaust / Tinput

Therefore :

Tinput = Texhaust / 1 - η ---- ( 2 )

where : Texhaust = 293 k ,   η = 0.50 ,

insert values into equation ( 2 )

Tinput = 293 / 1 - 0.50

           = 586 k

Calculate the new efficiency

The new efficiency of the ideal engine ;

η = 1 - T'exhaust / Tinput

  = 1 - 243 / 586

  = 1 - 0.41 = 59%

Hence we can conclude that the new efficieny is 59%

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