In large steam power plants, the feedwater is frequently heated in closed feedwater heaters, which are basically heat exchangers, by steam extracted from the turbine at some stage. Steam enters the feedwater heater at 1.6 MPa and 250°C and leaves as saturated liquid at the same pressure. Feedwater enters the heater at 4 MPa and 30°C and leaves 10°C below the exit temperature of the steam. Neglecting any heat losses from the outer surfaces of the heater, determine
(a) The ratio of the mass flow rates of the extracted steam and the feedwater heater and
(b) The reversible work for this process per unit mass of the feedwater. Assume the surroundings to be at 25°C.

Transcribed Image Text:

Steam 16 MPa from 250 C turbine Feedwater 4 MPa 30PC sat. liquid FIGURE P8-109