A rigid insulated vessel is divided into two equalvolume com

A rigid, insulated vessel is divided into two equal-volume compartments connected by a valve. Initially, one compartment contains 1 m^3 of water at 20 degree C, x = 50%. and the other is evacuated. The valve is opened and the water is allowed to fill the entire volume. For the water, determine the final temperature, in degree C, and the amount of entropy produced, in kJ/K.

Solution

Mass of water   = density * 1 m^3

density from steam tables @20 C x = 0.5    = 0.0346 kg/m^3

Pressure   = 2.34 kPa

initial entropy = 4480 J/kg K

mass of water = 0.0346 kg

final density of water after valve is opened   = 0.0346 / 2   = 0.0173 kg/m^3

Final Pressure = 2.34 kPa

from steam tables at 2.34 kPa and density = 0.0173 kg/m^3

we get superheated vapor at 20.3 C   (final temperature)

final entropy s2   = 8670 J/kg K

Change in entropy = m * (s2 - s1)

                           = 0.0346 * (8670 - 4480 )   = 144.974 J/K