Question

In cogeneration power plant with power load of 5.6 MW and heating load of 2 MW. Steam is generated at 40 bar and ${500}^{\circ }C$ and expanded isentropically to 0.06 bar. For process heating the steam is extracted at 2 bar and condensed to saturated liquid at 2 bar. Steam generation required to fulfill the requirement is ____ tonnes per hour.

At 40 bar, ${500}^{\circ }C$.

h = 3445.3 kJ/kg

s = 7.0901 kJ/kgK

• A. 16

Answer 1

The correct option is A 16

$h_1=3445.3kJ/kg$

$s_1=7.0901kJ/kgK$

$s_1=s_2=7.0901kJ/kgK$

$h_4=504.7kJ/kg$

$x_2=\frac{s_2-s_f}{{\left(s_{fg}\right)}_{2bar}}$

$x_2=\frac{7.0901-1.5301}{5.597}$

$x_2=0.9934$

$h_2={(h_f+x_2{h}_{fg})}_{2bar}=2692.14kJ/kg$

$x_3=\frac{s_3-s_f}{s_{fg}}=\frac{7.0901-0.5208}{7.815}=0.84$

$h_3={(h_f+x_3{h}_{fg})}_{0.06bar}=2054.77kJ/kg$

${\dot{m}}_1(h_2-h_4)=2\times {10}^3\Rightarrow {\dot{m}}_1=0.9143kg/s$

$\Rightarrow ({\dot{m}}_1+{\dot{m}}_2)(h_1-h_2)+{\dot{m}}_2(h_2-h_3)=5.6\times {10}^3$

$\Rightarrow {\dot{m}}_2(h_1-h_3)=4911.37\Rightarrow {\dot{m}}_2=3.532kg/s$

${\dot{m}}_1+{\dot{m}}_2=4.4463kg/s=16tonnes/hr$