MasteringPhysics: Homework #4-Google Chrome Secure l https://session.masteringph
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Question
MasteringPhysics: Homework #4-Google Chrome Secure l https://session.masteringphysics.com/myct/itemView?offsets next&assignmentProblemID-85283422; Homework #4 Problem 21.53 Resources « previous 6 of 7 next Problem 21.53 Part A The electric output of a power plant is 720 MW. Cooling water flows through the power plant at the rate 1.40 What is the power plant's thermal efficiency? Express your answer as a percentage. 108 L/hr. The cooling water enters the plant at 170°C and exits at 27.0° C Submit My Answers Give Up Continue Activate Windows Go to Settings to activate Windows 6:09 PM O Type here to search 41) ENG 9/24/2017 ^ EExplanation / Answer
The heat taken away by the water is Q = cp*m*T; m = 1.4*10^8 (L/hr) * 1.00 (kg/L) * 1/3600 (hr/s) = 3.9*10^4 kg/s
cp = 4.18 kJ/kg
Q = 4.18*3.9*10^4*(27.0 - 17.0) = 1.630*10^6 kJ/s = 1630 MW
Qout = 750 MW. Qin = 1630 + 750 Mw
The efficiency is
Qout/Qin = 750/(1630 + 750) = 0.315 or 31.5 %