Answer to Question #233501 in Mechanical Engineering for Adeel

Question

Steam at 15 bar and 250oC is expanded reversibly in a closed system to 5 bar. At this pressure the steam is just dry saturated. For a mass of 1 kg calculate the following.

i. The final volume.

ii. The change in internal energy.

iii. The work done.

Answer 1

a)

Pv=RT

v=$\frac{RT}{P}$

=$\frac{0.46*523}{5}$

=48.116m³

b)

∆u=Q-W

W=mRT₁ln($\frac{P_1}{P_2}$ )

=1*0.46*523ln($\frac{15}{5}$ )

=264.30J

Q=0

∆u=-264.30J

c)

W=264.30J