Question

Steam at 1.4MN/M² and of dryness fraction 0.7 is throttled to 0.11MN/M², determine the dryness fraction of the steam after throttling

Answer 1

Since the total heat of steam remains the same after throttling, the steam becomes drier. Since the dryness fraction of steam is high initially, then after throttling the steam gets superheated.

$x = \dfrac{1.4M\ Nm^{-2} - 0.11M\ Nm^{-2}}{0.11Nm^{-2}}×{0.7}$

$= \dfrac{1.29Nm^{-2}}{0.11Nm^{-2}}× 0.7= 8.21$