Answer:
(a)466.2 btu/lbm (b) 85.8%
Explanation:
We have given that turbine receives steam at 600 psi and 600°F
So [tex]P_1=600psi[/tex] and [tex]T_1=600^{\circ}F[/tex]
From the standard steam table at 600 psi and 600°F
[tex]h_1=1289.9btu/lbm\ and s_1=1.5325btu/lbm^{\circ}R[/tex]
Assuming the expansion is isotropic in nature so [tex]s_1=s_2[/tex]
At the exhausts [tex]P_2=1\ inch\ hg=0.491psi[/tex]
From the steam table at 0.491 psi and [tex]s_2=1.5325btu/lbm^{\circ}R[/tex]
[tex]h_2=823.7btu/lbm[/tex]
(a)So work done [tex]w=h_1-h_2=1289.9-823.7=466.2btu/lbm[/tex]
(b) Efficiency [tex]\eta =\frac{work\ done}{w_{ideal}}=\frac{400}{466}=0.858[/tex]=85.8%
