Hydraulic simulation of a system with fluid pills and spacers

[BPW363]

I need to simulate the time-varying pressure and flowrate in a complex piping system. The pipes connect storage tanks holding fluids that have very different density and viscosity. The overall system has manifolds, valves, pumps etc. The nature of the problem also means we must simulate the pressure pulsations caused by liquid compressibility. Does anyone know if any of the pipe hydraulics packages allow you to simulate fluid pills and spacers, and can they track where the pills are in the system?

Thanks

 

[1503-44]

This is the one I use. It will do that and more.

https://www.dnv.com/services/pipeli...d-performance-synergi-pipeline-simulator-5376

 

[BPW363]

Thanks @1503-44, Did you check out the alternatives, and can you share what they were? And what is the annual license fee? Given its application to pipelines I am wondering if it will deal with vertical runs of pipe, and annular flow.

 

[LittleInch]

This sounds a bit to me like process simulation just because you can?

All simulations need some sort of simplification and assumptions to make it work. Normally you try and work out the worst case and best case and everything in practice is somewhere in between.

I'm struggling to believe if the products are that dissimilar that you really want to have a multi product manifold system?

but that's just me being practical - I just know you can eat many hours of simulation modelling for little effect unless you're very careful.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[1503-44]

The only competition at the time was Pipeline Studio, now owned by Emerson. It was a long time since that decision was made. Synergie (formerly Stoner Pipeline Simulator) was selected because it was the only such program that was approved for use by many major oil and gas companies at that time. I had also used it for a number of years prior to the time of the study, so there was no learning curve. Other than that, both had similar capabilities and were competitive in price. I do not know what the licensing schemes or costs of either program is today. Do not expect a bargain basement purchase. I imagine a short term lease would be 5,000/mo today, but I do not know. They now probably have various modules to buy with prices corresponding to how much you put into your shopping cart.

Synergie can model anular flow of one product at a time, but since it isn't practical to run a pipeline with multiple products with anular flow characteristics simultaneously, you're probably good with that. You can define a number of thermal conditions. It will model multiple products and interface generation between batches of products moving through a pipeline (is pills what you call batching?). Anular flow is modeled by defining shear rate and heat conduction and convection properties of the fluid. It will not do two-phase flow, but can approximate slack line flow conditions going downslope. It will model centrifugal pump dynamics and recip and centrifugal compressors and dynamics of control valves, sensors, transmitters, PIDs and relays. You can define diesel engine starts and stop sequences, when to open or close valves, etc. You can make graphic displays of the current state of your model or your real time system as it can receive current states of your system via SCADA input, and dynamically model your system in current or quick time look-ahead modes. You must select between liquid, or gas system models, as it will not do both simultaneously.

I do not know the current capabilities of Pipeline Studio...

http://www.energy-solutions.com/products-2/pipelinestudio/

 

[BPW363]

Hi LittleInch, thanks for the comments. I appreciate what you say about simulation, as George Box once said 'all models are wrong, but some are useful'. I think you would be surprised at how the world of engineering is being forced to change by advances in computer science. Slide-rule, followed by Hewlett-Packard, engineering had its place in the 1980s when I graduated, however, today we routinely run FEA and CFD. IoT and IT/OT is about to force engineers to rethink how we do simulation and why.

In my case, there are some specific operating scenarios that warrant what I'm describing. However, I've struggled to find a software package that deals with the specific problem. Instead, engineers are bolting together results from simple boundary case analysis, and phenomenological models in order to design hugely expensive systems. We then cut and paste the design hundreds of times and make Operations sort out the quirks and live with the inefficiencies. As regards batch fluid processing through the same manifold, in this case there is no economical alternative. I suspect there are many more cases if we go looking.

 

[BPW363]

1503-44: thanks for the PipeLine Studio reference, I'll take a look. I note both are pipeline software packages and wonder to what degree that would limit its use in piping system? Any thoughts are welcome. As regards pills vs. batching, I started out using 'pills' but couldn't find significant use of that term, in some ways saying 'slugs' of fluid makes more sense, but that term is used to describe multi-phase flow. Batching is the term used in Stoner PS so I switched - let me know if that seems wrong.

 

[1503-44]

Batching and running batch "trains" down the pipeline are understood by all.
Slugging is a one off shot into a pipe. Slug it with 50 bbls of diesel.

Stoner is set with miles or km of pipe as the default length unit and 1000s BBLS per day or m3/h flow rates but you can select other built in units, or define and use your own units, in3/fortnight if you want.

The data entry validation routine will flag large values for in-plant work, but again you can reduce, or increase those warning limits as you prefer.

It allows use of two kinds of pipe, transfer lines and headers. Headers do not keep tabs on changes of liquid volumes inside due to pressure or temperature, whereas transfer lines do. Thus headers are reserved for short pipe segments where "line packing" effects are insignificant, but you can use short transfer lines if you want to at a slight computation time penalty. I dont really notice any difference.

I have used SPS to model multiproduct distribution terminals with up to 22 tanks.

There are some in-plant specific models out there, but I think they do not have any transient flow capability. Just volume in = volume out stuff.

I like the George Box quote.

Is there a specific class of problems that you are trying to address, or just transient analysis in general?

 

[BPW363]

1503-44 For me it makes sense to refer to batching and trains. While it makes sense to talk of slugs of fluid it will confuse some audiences. I am looking at the case of transient flow in its most general sense including 'batched' compressible flow. One missing piece of the puzzle is fluid mixing at the interfaces - does Synergi deal with that phenomena when running trains?

As for George Box, were it not for the genius of RA Fisher he would be better know among engineers. He's the father of meaningful debates on heuristics and model fidelity: and provides a nice riposte for simulation skeptics ;-)

 

[1503-44]

It does composition tracking in liquid and gas. There is an EOS that allows diffusion modeling by FMV and another that tracks by batch name. You can choose one or the other, depending on if interest is primarily batch tracking, or knowing the properties of a lineup of fluids. Both use a "slightly compressible" liquid modeling technique.

From the user guide...

Any number of batches of any number of different fluids may be defined to coexist in one simulation, and these batches move in accordance with the flow rate in the equipment. They may blend where two different batches come together, the mixture resulting in a possible curved concentration profile in pipes fed by a point of blending. Batches and compositions are tracked using fluid mixture vectors (FMVs). An FMV is the composition at a point; the composition between two FMVs is the linear interpolation of the composition at the FMVs. This means that the program represents continuously changing fluid properties with a very small number of FMVs, provided the fluid properties change in a basically linear fashion.

The TRIVC variable (minimum change in concentration) and TRIVB variable (minimum batch size), set through the equation of state, determines whether a new FMV is created. TRIVC is used as a relative tolerance—if the concentration of a single component or fluid changes by a half percent out of linear, then a new FMV is created to preserve the non-linearity. In addition, two FMVs should not be closer than the TRIVB volume. The number of FMVs in a system affects the time step. The time step is adjusted so that a FMV reaches the pipe end exactly at the end of a time step. Therefore, equipment at the pipe end uses the appropriate composition. For liquid systems, each FMV does not necessarily represent a new batch. New batches are launched when the controlling fluid changes based on the mass fraction or the mixing weight parameters.

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