Valve Pressure problem in Hysys

[maabdolat]

Hi....

i have a question regarding Hysys, kindly help me out....


I designed a centrifugal pump with discharge pressure of 500Kpa for pumping sulfur
in Steady Sate mode of Hysys.... i achived it perfectly

Now i want to place a valve with 100% opening at discharge line of pump with Delta Pressure of 100 Kpa, so that after valve pressure would become 400Kpa
uptill now, it is fine in Steady State mode...

Now, i switch to dynamic mode, it works fine there too and discharge pressure is 400Kpa

but the confussion for me is, if i switch to dynamic mode before placing valve on discharge line of pump

and put a valve in dynamic mode instead of steady state mode, the delta Pressure of Valve at 100% opening is automatically calculated and is very high....


now, i am confussed , which method of Hysys is correct

1. Place valve in steady state , put manually deltaPressure of valve and then switch to dynamic mode
or
2. Place valve in Dynamic mode and let Hysys to calculate delta Pressure of Valve....


kindly help me out.... i am much confussed about this behaviour of Hysys....

regards,

[raybk2000]

You need to size the valve; i.e. input an equivalent valve CV in dynamic. Otherwise, Hysys may auto calculate a cv from steady state input dp and flow and this cv can be very small. When running with this valve cv in dynamic, the dp is too high if flow increases.