3 replies to this topic

[abduabd]

Hello community,

I am a recent Chemical Engineering graduate interning at a petrochemical company and my latest project involves performing sensitivity analyses on different pipeline networks. I have a couple of questions;

1. I know HYSYS isn't very good at simulating pipeline pressure drops, but, for preliminary assessment, when HYSYS gives the warning "Increment dp > 10%. Check Trace" . . . what does this mean, even though the simulation converges? I have observed that I usually get this warning when I have a high dP to outlet pressure ratio (I could be wrong). Does anyone know what basis HYSYS uses when determining this?

2. When I am done running my simulations in HYSYS, I would like to transfer my pipeline data to PIPEPHASE to run more rigorous calculations. Does anyone know what flow correlations in HYSYS align best with the results obtained in PIPEPHASE? (In HYSYS, I use the default Beggs & Brill corellations).

I only just discovered this forum recently and have already learned so much from it. Many thanks.

[Chellani]

Hi,

Here is my guess for your first query.
Estimation of delta P requires physical properties and vapor fraction and both of them are dependent on system pressure so it becomes and iterative problem.
Hysys divides pipe segments into few segments/increments based on the number of increments being used as input (it is available on Rating \ Sizing page of pipe unit op). At any point of time if delta P over a segment is huge (looks > 10% of inlet pressure) it gives you a warning message because your results may be incorrect i.e. you are using low number of segments / iterations to solve the problem hence you should increase number of increments so that evaluation of physical properties and delta P would be done more number of times which eventually can increase your time for convergence.
So if you see this warning message, increase number of increments of pipe.

For your second query, no correlation would give you 100% correct results as all of them are empirical and some of them may be good for few system / range and other ones may be good enough over a different range. Default one i.e. Beggs and Brill may be a good starting point.

All the best.

[abduabd]

Thank you, so much. I had almost given up hope that anyone would respond. I tried increasing the number of increments for the pipeline to a ridiculously high number, but I still got the warning. Carrying out the calculations manually, though, gave results consistent with the converged results from HYSYS, so, I will make the assumption that the HYSYS results are acceptable.

Thanks, again.

[Boualem]

Thak you so much for your help