Answer:
(a) Volume of the tank is
(b) Temperature is
Pressure is 21.3 kPa
(c) The change in internal energy is 1373.54 kJ/kg
Solution:
As per the question:
Mass of liquid in the tank, m = 1.4 kg
Temperature, T =
Volume occupied by water, V = 25% = 0.25
Volume occupied by air, V' = 75%
where
= Volume of tank
Now,
(a) In order to calculate the volume of the tank, we make use of the steam table for specific volume at as given temperature:
At , the specific volume, v = 0.001157
At , the internal energy, u = 850.46 kJ/kg
Now, Volume of water, V = mv =
Thus
(b) For the final temperature and pressure, we calculate the specific volume, v' and then find the corresponding temperature and pressure from the steam table:
v' =
The corresponding temperature to this specific volume, T' =
The corresponding pressure to this specific volume, P' = 21.3 kPa
The corresponding internal energy to this specific volume, u' = 2224 kJ/kg
(c) The change in the internal energy of water is given by: