A steam power plant receives heat from a furnace at a rate of 280 GJ/h. Heat losses to the surrounding air from the steam as it passes

A steam power plant receives heat from a furnace at a rate of 280 GJ/h. Heat losses to the surrounding air from the steam as it passes through the pipes and other components are estimated to be about 8 GJ/h. If the waste heat is transferred to the cooling water at a rate of 145 GJ/h, determine (a) net power output and (b) the thermal efficiency of this power plan

Answers

a) dot W_{out} = 35.278,MW, b) eta_{th} = 45.357,%

Explanation:

a) The net power output is:

dot W_{out} = dot Q_{in} - dot Q_{out} - dot Q_{loss}

dot W_{out} = left(280,frac{GJ}{h} - 145,frac{GJ}{h} - 8,frac{GJ}{h}right)cdot left(frac{1000,MJ}{1,GJ}right)cdot left(frac{1,h}{3600,s} right)

dot W_{out} = 35.278,MW

b) The thermal efficiency of the power plant is:

eta_{th} = frac{dot Q_{in}-dot Q_{out} - dot Q_{loss}}{dot Q_{in}}times 100,%

eta_{th} = frac{280,frac{GJ}{h}-145,frac{GJ}{h}-8,frac{GJ}{h} }{280,frac{GJ}{h} } times 100,%

eta_{th} = 45.357,%

Yes

Explanation:

Yes steam power plant is heat engine.

As we know that a heat engine takes from source heat and produce some amount of work and reject the heat to the sink.

So the steam power plant fulfill the all requirement like it take heat from boiler and produce some amount work and then reject the heat by using condenser.So we can say that steam power plant is an example of heat engine.

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