contestada

Two hundred litres of wet steam at 250°C has an entropy of 25 kJ/K. Determine the steam quality and mass of steam.

Respuesta :

Answer:93 %

Explanation:

Given

Volume(V)=200 L

entropy=25 KJ/K

At [tex]T_{sat}=250 ^{\circ}[/tex]

Properties are

[tex]s_f=2790 J/kg-K[/tex]

[tex]s_g=6070 J/kg-K[/tex]

[tex]\rho _g=20 kg/m^3[/tex]

[tex]\rho _f=799 kg/m^3[/tex]

Entropy at \eta quality is given by

[tex]\frac{S}{m}=s_f+\chi s_{fg}[/tex]

[tex]\frac{25}{m}=2790+\chi \left ( 6070-2790\right )[/tex]

[tex]\frac{25}{m}=2790+\chi \left ( 3280\right )----1[/tex]

Also for mass

[tex]\left ( \frac{m}{V}\right )^{-1}=\rho _f^{-1}+\chi \left ( \rho _g^{-1}-\rho _f^{-1}\right )[/tex]

[tex]\left ( \frac{m}{0.2}\right )^{-1}=799^{-1}+\chi \left ( 20^{-1}-799^{-1}\right )[/tex]

[tex]\left ( \frac{0.2}{m}\right )=1.25\times 10^{-3}+\chi \left ( 0.04875\right )---2[/tex]

From 1 and 2

we get

m=4.3 kg

[tex]\chi =0.93[/tex] or 93%