4 replies to this topic

[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,
 

[equilibrium]

I think the specifications of your valve are unreasonable.  100% open, where is the control?

[Maabdolat]

dear u didnt read my post clearly, i just want to ask... why hysys interperate  different pressure in steady state or dynamic state....

[thorium90]

I think the question is itself confusing and unclear. Words like "which method of hysys is correct", makes no sense since the user is the one creating the inputs. (Garbage In Garbage Out, as Art mentions... Don't blame hysys for giving you weird answers if you input weird stuff). There is also missing information like the valve Cv that was input.

 

Perhaps you could upload screenshots of the problem or post your file for viewing?

 

I think your weird questions arise because you are not sure how to use hysys dynamics. Perhaps you could watch a nice youtube video to learn some basics first.

Edited by thorium90, 19 October 2013 - 04:49 AM.

[Alexsandres]

Dear Maabdolat,

 

As far as I know, when we're working on steady state, we don't need any flow coefficient of control valve. However, when we change to dynamic mode, we have to defined the flow coefficient of the control valve.

 

Thus, on steady state, we have to clearly state (and calculate) the flow coefficient for your system. Upstream is 500 Kpa and downstream is 400 Kpa, set opening valve on 100% and you'll get flow coefficient.

 

You might input wrong flow coefficient (CV) on your control valve, thus dynamic mode interprets wrong direction (which than made you confusing). But if, you input correct CV value, dynamic mode should predict correctly. On your case, if you open 100% opening, pressure drop should be around 100 Kpa, as close as on steady state) 

 

Hysys pressure drop calculation approach on steady state and dynamic should be same, and not confusing at all.

 

Hope that helps. Correct me if I'm wrong.