A 1500 kW heat engine operates at 25% efficiency. The heat energy expelled at low temperature is absorbed by a stream of water that enters cooling coils at 20.°C. The flow rate of the water is 60. L/s. Determine the temperature of the water as it leaves the cooling coils... Any ideas?
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Energy entering the engine
1500 kW / 0.25 = 6000 kW
1500 kW is converted to usable energy
6000 - 1500 = 4500 kW
is exhausted to the cooling stream
4500 kW = 4500 kJ/s = 4.5(10^6) J/s
heat capacity of water is 4186 J/kg°C
one liter of water is approximately a kg
4.5(10^6) J/s / 60 kg/s / 4186 J/kg°C = 17.9°C temperature rise
water exits at
20 + 17.9 = 38°C
1500 kW / 0.25 = 6000 kW
1500 kW is converted to usable energy
6000 - 1500 = 4500 kW
is exhausted to the cooling stream
4500 kW = 4500 kJ/s = 4.5(10^6) J/s
heat capacity of water is 4186 J/kg°C
one liter of water is approximately a kg
4.5(10^6) J/s / 60 kg/s / 4186 J/kg°C = 17.9°C temperature rise
water exits at
20 + 17.9 = 38°C