Question

A nonconducting tank of negligible heat capacity and 1 m3

volume is connected to

pipeline containing steam at 5 bar and 370℃, filled with steam to a pressure of 5 bar,

and disconnected from the pipeline. If the tank initially contains steam at 1 bar and 150℃, how much steam is in the

tank at the end of the filling process, and what is its temperature?

Note: The answer is 1.56kg and 425c but I can’t figure out how to get that

Answer 1

initially contains steam at

Pressure P = 1 bar

Temperature T = 150℃

At initial conditions

Specific volume = 1.9364 m3/kg

Specific internal energy = 2582.8 kJ/kg

Initial mass = initial volume / Specific volume

= 1 m3 / 1.9364 m3/kg

= 0.5164 kg

From the mass balance equation

M2 = M1 + Msteam

From the energy balance equation

Assume the different values of T2

V2' = V2 /M2

Difference between V2' & V should be less than 3%

For trials and error, we get T2 = 425°C

Pressure P2 = 5 bar

Final conditions

Specific internal energy = 3004.5 kJ/kg

Specific volume = 0.6407 kg/m3

Mass of steam = 1.0628 kg

M2 = 1.56 kg