Question

A steam power plant receives heat from a furnace at a rate of 300 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 16 GJ/h. If the waste heat is transferred to the cooling water at a rate of 140 GJ/h, determine (a) net power output and (b) the thermal efficiency of this power plant.

Answer 1

Net Power output 144 GJ/h

`\eta = 51.41 %`

Step-by-step explanation:

Given data:

Heat received = 300 GJ/h

`= (300* 10^9)/(3600) J/s`

`= 77.78 * 10^6 W`

Heat lost
`Q_2 = 16 GJ/h`

Heat to the water
`= Q_3 = 140 GJ/h`

Net Power output
`= Q_1 - Q_2 -Q_3`

= 300 - 16 - 140

= 144 GJ/h

`=(144* 10^9)/(3600) = 40* 10^8 J/s`

thermal efficiency

`\eta = (net\ power)/(heat\ supplied)`

`= (40* 10^6)/( 77.78 * 10^6)`

= 0.514 = 51.41 %