The Carnot cycle can be shown to be- the most efficient thermodynamic cycle for

Question

The Carnot cycle can be shown to be- the most efficient thermodynamic cycle for given tempera-t tures. How efficient would a Carnot heat engine be operating between reservoirs at 20degreeC and 500degree C? This coule be something like a power plant. What would the coefficient of performance be for a Carnot refrigerator operating between reservoirs at 20degreeC and 35degreeC? This could be something like an air conditioner (c) If the low temperature reservoir is at 20degreeC. how high would TH have to be to have a Carnot efficiency of 90%?

Explanation / Answer

a) Use equation,

Efficiency,  n = 1- Tc/Th = 1-  20/ 500 = 0.96  = 96%

b) Use equation
KOP  =  Qc/W  = Tc/(Th - Tc) = 20/(35-20) = 1.33

c) Use equation ,

Efficiency,  n = 1- Tc/Th

0.90 = 1- 20/ Th    =>  Th = 200 C

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