3 replies to this topic

[ayan_dg]

I want to do a simple simulation in HYSYS

Inlet steam specification:
Steam
Temp- 385 C
Pressure: 45.9 kg/cm2 g
Flow rate : 50 te/hr

Valve opening: 50 %

Outlet :
steam
Pressure- 4.1 kg/cm2 g
Temp- Predicted by HYSYS

the valve is a Pressure control valve controlling Pressure of Output stream at 4.1 kg/cm2 g

I want to know if the valve gets 70 % open what will be the pressure & temp downstream

[Zauberberg]

I'm not sure if I understood your question in a correct manner, but here is what will happen if we are thinking about the same thing: pressure downstream of control valve is unchanged, and higher valve opening is just a consequence of increased steam demand. Therefore, resulting temperature will be the same as in 50% valve opening case - simply calculated by isenthalpic flash - as long as both pressures upstream and donwstream of control valve are unchanged. Is that your query?

[ayan_dg]

I'm not sure if I understood your question in a correct manner, but here is what will happen if we are thinking about the same thing: pressure downstream of control valve is unchanged, and higher valve opening is just a consequence of increased steam demand. Therefore, resulting temperature will be the same as in 50% valve opening case - simply calculated by isenthalpic flash - as long as both pressures upstream and donwstream of control valve are unchanged. Is that your query?

Actually what i intend to simulate is what will happen downstream if Automatic control of pressure is lost and the valve inadvertantly open fully.

[Padmakar Katre]

Dear,
As far as Hysys Dynamics is concerned Hysys recommends you to specify the P-F dynamic specication i.e. pressure-flow relationship. So once you put your controller in manual mode of operation and give the manual output the result will be varied flow based on the Cv calculated in the Dynamics tab of the Valve operations based on the user inputs options. It keeps the discharge presure constant. I hope this will clear your doubt. Waiting for your comment.
In Dynamics you cannot specify flow in your case its 50000 in case of P-F specifications. What you can do is specify the flow in order to intialize the stream and once you switch to dynamics flow will ba calculated accoring to the Control valve Opening its Cv and all.