Question

A steam powe cycle with regneration as shown below on the $T-s$ diagram employs a single open feedwater heater for efficiency improvement. The fluids mix with each other in an open feedwater heater. The turbine is isentropic and the input (bleed) to the feedwater heater from the turbine is at state $2$ as shown in the figure. Process $3-4$ occurs in the condenser. The pump work is negligible. The input to the boiler is the state $5$. The following information is available from the steam tables:
3350

State	$1$	$2$	$3$	$4$	$5$	$6$
Enthalpy $kJ/kg$	$3350$	$2800$	$2300$	$175$	$700$	$1000$

The mass flow rate of steam bled from the turbine as a percentage of the total mass flow rate at the inlet to the turbine at state $1$ is

• A. 20

Answer 1

The correct option is A 20


From energy balance equation
$m{h}_2+(1-m)h_4=h_5$
$m{h}_2+m{h}_4+h_4=h_5$
$m(h_2+h_4)=h_5-h_4$
$m=\frac{h_5-h_4}{(h_2-h_4)}$
$m=\frac{700-175}{(2800-175)}\times 100$
$=0.2or20$%