2 replies to this topic

[babukannan]

How to model a Flow totalizer in hysys for dynamic simulation?

[Dacs]

You can trick Hysys to simulate totalizer by using some circular references in the Hysys built-in spreadsheet.

 

Step by step procedure:

• Add one spreadsheet, for this discussion, we'll name it "SS A"
• Add another one, name it "SS B"
• Go to SS A and import the variable (for this discussion, mass flowrate with units of kg/hr) from your target material stream to cell B1 (you can place it in any cell but I suggest to follow this so you can see the sequence at hand easier)
• Go to Integrator, and take hold of the step size (let's say it's 0.1 seconds)
• Go back to SS A and place this value in B2
• Still on SS A, make a formula in B3 to convert B2 (which has a unit of seconds) to the time unit of your flowrate (per hour in this case). so you need to input "=B2/3600" in cell B3 to convert the time step from seconds to hours.
• Still on SS A, in cell B4, input this formula "=B1*B3". This calculates the equivalent mass considered for the selected stream for a given integrator step size.
• Still on SS A, place a value of zero in cell B5
• Still on SS A, go to cell B6 and input "=B4+B5"
• Go to SS B, go to B1 and import cell B6 from SS A
• Go back to SS A, go to cell B5 and import cell B1 from SS B. This will create a circular loop. It normally flags an error if you do it within a spreadsheet, but it doesn't seem to be when doing across spreadsheets.

Things to consider:

• I tried looking for a totalizer within built-in functionality in Hysys, but I haven't found one. I was forced to be creative and made this and while it's not elegant, it works (at least with my dynamic models built for v7.3).
• This seems to work only on one integration pass (resetting the integrator does not reset the value), so you may have to rework the formulas (specifically deleting import variable in SS A cell B5, placing a value of zero, and reimporting the same variable) whenever you reset your integrator or simply want to reset the totalizer back to zero
• It's imperative that the step size value in SS A cell B2 is the same value that's used by the integrator, otherwise you'll make a gross error in tracking the totalizer function. It goes without saying that whenever you change your step size, you need to change SS A cell B2 to match

There must be a more elegant way of doing this, but if you just want to do a quick totalizer functionality, this should do.

 

Please let me know how it works out for you.

Edited by Dacs, 04 January 2016 - 01:11 AM.

[Lucian Gomoescu]

Hello,

I want to mention that, starting with Aspen HYSYS 2006, Aspentech offers a new great feature that solves in an easy way the problem of not having a totalizer block. This feature is called Integrator and belongs to Transfer Function block.
I attached some snapshots for two simple examples:
1. A mass totalizer has to record the total mass from time 0 to time 1 h for stream 1 which has a constant flow rate of 100 kg/h.

 

I used a transfer function block as in the pictures.

 

2. A mass totalizer has to record the total mass from time 0 to time 1 h for stream 1 which has a ramp flow rate from 0 to 100 kg/h in one hour.

I used the same transfer function block as in example 1 + a second one for defining the ramp.

The results are found in the attached ppt.

In conclusion, the integrator term of the F.T. block is a great tool for integrating in time the values of a stream or unit.

Happy New Year,
Lucian

Attached Files

•  Mass Totalizer.pptx   168.67KB   32 downloads