Question

An ideal reheat Rankine cycle operates between the pressure limits of $10kPa$ and $8MPa$, with reheat being done at $4MPa$.The temperature of steam at the inlets of both turbines is ${500}^{o}C$ and the enthalpy of steam is $3185kJ/kg$. Use the following table for relevant data.

Super heated steam temperature ${(}^{o}C)$	Pressure $\left(MPa\right)$	$v$ $\left(m^3/kg\right)$	$h$ $\left(kJ/kg\right)$	$s$ $\left(kJ/kgK\right)$
$500$	$4$	$0.08644$	$3446$	$7.0922$
$500$	$8$	$0.04177$	$3399$	$6.7266$

Disregarding the pump work, the cycle efficiency (in percentage) is

• A. 40.73

Answer 1

The correct option is A 40.73


Given,
$p_2=10kPa;p_1=8MPa$
$p_3=4MPa;h_2=3185kJ/kg$
$h_4=2247kJ/kg;h_1=3399kJ/kg$
$h_3=3446kJ/kg;h_6=191kJ/kg$
$w_T=(h_1-h_2)+(h_3-h_4)$
$q_s=(h_1-h_6)+(h_3-h_2)$
$\therefore W_T=(3399-3185)+(3446-2247)$
$=1413kJ/kg$
$q_s=(3300-191)+(3446-3185)$
$=3469kJ/kg$
$\eta =\frac{1413}{3469}=0.4073$
$=40.73$%