A coal-fired power plant converts one-third of the coal's energy into electrical energy. The electrical power output of the plant is 1000 MW. he other two-thirds of the energy content of the fuel is rejected to the environment as waste heat. About 15% of the waste heat goes up the smokestack, and the other 85% is taken away by cooling water that is drawn from a nearby river. The river has an upstream flow of 100 m ³ /s and an upstream temperature of 20 C. The specific heat of the water is 4184 J/(kg C). 1MW =10 ⁶ J s ^-1 .

a) If the cooling water is only allowed to rise in temperature by 10 C, what flow rate from the river (Q _c ) is required?

b) The power plant returns the cooling water back to the river. What is the river temperature just after it receives the heated cooling water (Ts)?

Transcribed Image Text:

Coal 3,000 MW, Q₁=100.0 m³/s T=20.0 °C Electrical output 1,000 MW 33.3% efficient steam plant Stream Stack heat 300 MW, Cooling water 1,700 MW, Qc= T=30.0 °C 2₁-100.0 m/s T₁= Coal 3,000 MW, Q₁=100.0 m³/s T=20.0 °C Electrical output 1,000 MW 33.3% efficient steam plant Stream Stack heat 300 MW, Cooling water 1,700 MW, Qc= T=30.0 °C 2₁-100.0 m/s T₁=

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