Practical steam engines utilize 537°C steam, which is later exhausted at 244°C.

Question

Practical steam engines utilize 537°C steam, which is later exhausted at 244°C.

(a) What is the maximum efficiency that such a heat engine can have?
_____%

(b) Since 244°C steam is still quite hot, a second steam engine is sometimes operated using the exhaust of the first. What is the maximum efficiency of the second engine if its exhaust has a temperature of 150°C?
_____%

(c) What is the overall efficiency of the two engines?
______%

Question 2

What is the coefficient of performance of an ideal heat pump that has heat transfer from a cold temperature of -27.0°C to a hot temperature of 38.0°C?

_____

Question 3

A certain gasoline engine has an efficiency of 28.0%. What would the hot reservoir temperature (in °C) be for a Carnot engine having that efficiency, if it operates with a cold reservoir temperature of 190°C?

_____°C

PLEASE ANSWER ALL THE QUESTIONS DONT GIVE ANY WRONG ANSWERS THANKS FOR YOUR HELP !

Explanation / Answer

Question 1:

a) Efficiency = (1 - (Tc/Th))*100%

Tc = 244 + 273 = 517 K

Th = 537 + 273 = 810 K

Efficiency = (1 - (517/810))*100% = 36.17 %

b) Tc = 150 + 273 = 423 K

Th = 244 + 273 = 517 K

Efficiency = (1 - (423/517))*100% = 18.18 %

b) Overall efficiency = (1 - (423/810))*100% = 47.78 %

Question 2:

coefficient of performance = 1/efficiency

efficiency = 1 - (246/311) = 0.209

coefficient of performance = 1/0.209 = 4.785

Question 3:

28 % = (1 - (463/Th))*100%

Th = 643.06 K = (643.06 - 273) oC = 370.06 oC

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