5 replies to this topic

[Amiemashad]

Hello all,

I need to calculate the time delay in a process, for instance I want to change the temperature in the starting point of the pipe and see how much time does it take to change the temperature of pipe ending point

Thx in advance

[Zauberberg]

You need to switch to Dynamics mode, and have all piping segments defined - pipe diameter, length, elevation, fittings, insulation, ambient temperature etc. Then you can easily create a stripchart showing changes of any of the parameters of interest, by time.

[Amiemashad]

You need to switch to Dynamics mode, and have all piping segments defined - pipe diameter, length, elevation, fittings, insulation, ambient temperature etc. Then you can easily create a stripchart showing changes of any of the parameters of interest, by time.

Thanks for your reply, and i did it for a separator, but as soon as i changed the molar flow in the input, the molar flow in the output was changed without any delay. but i think it should have delay !!!!! ?

[Zauberberg]

Not necessarily in my opinion. If the pipeline system is under its operating pressure and with full contingency, introducing higher flow from the starting point will result in displacing the same volume at the other end, i.e. you'll get the same flow at both ends. It's a continuity principle.

Different results I would expect if e.g. you have a system that has to be pressurized first, then you might have the case of continuously increasing flow - and again depending on whether you pressurize the system first up to the operating pressure and then open the valve (start the flow), or the flow begins to develop as soon as fluid is introduced into the system.

[PaoloPemi]

there must be a delay (which is related with speed of sound in fluid) but you need to define the partial differential equations for the system and a proper method (say method of characteristics or equivalent) to convert into total differential equations and solve the problem, which is a not easy.
I am not familiar with your simulator and I do not know which methods are applied in dynamic simulations, as far as I know for columns it's time integration, if it is the same for pipelines you can't expect those capabilities.

[hshethna]

There has to be a hold up in the separator or the pipe in HYSYS for you to see the time delay.
Look at the holdup that you provided. Must be very small.