ME 3320: Thermodynamics II Handout #10

Homework #10: Problems 10-14, 10-34,10-46,10-70E,10-84

10-44 The closed feedwater heater of a regenerative Rankine

cycle is to heat 7000 kPa feedwater from 260°C to a saturated

liquid exiting the mixing chamber. The turbine supplies bleed

steam at 6000 kPa and 325°C to this unit. This steam is

condensed to a saturated liquid before entering pump 2. Calculate

the amount of bleed steam required to heat 1 kg of feedwater in

this unit.

10-46 Repeat Prob. 10-45 by replacing the open feedwater

heater with a closed feedwater heater. Assume that the feedwater

leaves the mixing chamber at the condensation temperature of the

extracted steam and that the extracted steam leaves the heater as a

saturated liquid and is pumped to the line carrying the feedwater.

10-69 Steam enters the turbine of a cogeneration plant at 4 MPa

and 500°C. One-fourth of the steam is extracted from the turbine

at 1200-kPa pressure for process heating. The remaining steam

continues to expand to 10 kPa. The extracted steam is then

condensed and mixed with feedwater at constant pressure and the

mixture is pumped to the boiler pressure of 4 MPa. The mass

flow rate of steam through the boiler is 55 kg/s. Disregarding any

pressure drops or the heat losses in the piping, and assuming the

turbine and the pump to be isentropic, determine the net power

produced and the utilization factor of the plant.