Pressure vessel modeling

[lordgogi]

Hello,

I I need to simulate emergency draining of a steam generator (using Octave). I have a pressurized tank: 3m³in total. Pressure in the vessel is 40 bar(a).Inside the vessel there is 2.2 m³ of saturated water (at 40 bar) and the rest of the volume is filled with steam (also at saturation at 40 bar). The essel is perfectly insulated.

Let's say i open the valve and start draining the boiler at constant rate of 54kg/s. I need to know what is the state of the boiler when I drain all the water. I derived these equations:

(dm/dt) = const.
(dE/dt) = (dm/dt) * e_w(p)
m = m_w + m_e
E = m_w * e_w(p) + m_st * e_st(p)
V_total = v_st(p) * m_st + v_w(p) * m_w


where:

m = total mass in the Steam generator [kg]
E - total enthalpy of the Steam generator [kJ/kg]
dt = time inkrement
m_w = mass of water in the Steam Generator [kg]
m_st = mass of steam in the Steam Generator [kg]
e_w = enthalpy of water in steam generator [kJ/kg]
e_st = enthalpy of steam in the Steam Generator [kJ/kg]
V_total = Volume of boiler [m3]
v_w = specific volume of water in steam generator [m3/kg]
v_st = specific volume of steam in the Steam Generator [m3/kg]


I thus expect the Steam generator to reach phase thermal equilibrium at every point of my time scale.

Is this the best way how to calculate it:? Or am I missing something. Do you have any suggestions how to make my model more realistic with respect to real world scenario????? Maybe I am missin some work that system has to do to push the water through the valve....or not??


Thank you all very much for answers.