1)A small-scale steam engine might operate between the temperatures of 20C and 3

Question

1)A small-scale steam engine might operate between the temperatures of 20C and 300C,

with a maximum steam pressure of 10 bars. Calculate the eciency of this engine according

to the steam engine (a.k.a. Rankine) cycle.

2)Suppose you are told to design a household air conditioner using HFC-134a as its working

substance. Over what range of pressures would you have it operate? Explain your reasoning.

Calculate the COP for your design, and compare to the COP of an ideal Carnot refrigerator

operating between the same reservoir temperatures.

Explanation / Answer

given that T1= 2400c = 240+273= 513K T2= 200c = 20+ 273 = 293K effeicency = e = 1-T2/T1 = 1-293K/593K = 0.43%    given that T1= 2400c = 240+273= 513K T2= 200c = 20+ 273 = 293K effeicency = e = 1-T2/T1 = 1-293K/593K = 0.43%    = 1-293K/593K = 0.43%   

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