1) At a steam power plant, steam engine work in pairs, the heat output of the fi
ID: 1484856 • Letter: 1
Question
1) At a steam power plant, steam engine work in pairs, the heat output of the first one being the approximate heat input of the second. The operating temperature is first 627 degrees Celsius and 427 degrees Celsius, and of the second 407 degrees Celsius and 277 degrees Celsius. Assume the efficiency of the engines is 65% of the ideal (Carnot) efficiency. What is the efficiency for the first engine?
A) 0.32 B) 0.22 C) 0.65 D) Need more information
2) In the above problem, at what rate must coal be burned to put out 10^9 watts of power. The heat of combustion of the coal is 2.8x10^7 J/ kg? (Note: Watt=J/s)
A) 360 kg/s B) 36 kg/s 55 kg/s D) Need more information
Explanation / Answer
1) efficiency = (1 - (Tc/Th))= (1 - (427/627)) = 0.32
2) Rate of burning the coal = 10^9/(2.8*10^7) = 36 kg/s
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