A steam power plant receives heat from a furnace at a rate o

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) the net power output and (b) the thermal efficiency of this power plant. Determine the COP of a refrigerator that removes heat from the food compartment at a rate of 5040 kJ/h for each kW of power it consumes. Also, determine the rate of heal rejection to the air.

Solution

7-38

Rate of heat removal = 5040 kJ/h

= 5040 / (60*60) kJ/s

= 1.4 kW

COP = Rate of heat removal / Power input

= 1.4 / 1

= 1.4