Question

You have a rigid, sealed container of water and steam at a gauge pressure of 50 kPa. The initial mass of the mixture is initially 25% liquid and 75% vapor. You add heat until the mixture is pure vapor. Find the final guage pressure.

Answer 1

The final gauge pressure is 70 kPa

Solution:

As per the question:

Gauge pressure, P = 50 kPa = 50000 Pa

Now,

The specific volume is given by:

v =
`v_(f) + xv_(g)`

where

x = 0.75

Using saturated vapor- pressure table,

At a pressure of 50 kPa

`v_(f) = 0.001030 m^(3)/kg`

`v_(g) = 3.2403 m^(3)/kg`

Thus

v_{g} = 0.001030 + 0.75\times 3.2403 = 2.431255

Now,

The final gauge pressure is the pressure (saturation) which corresponds to the value of
`v_(g)`

Thus at
`v_(g) = 2.431255`

Final Pressure, P' = 70 kPa