Simscape pipe cleaning model - cleaning used pipe's interior surface with different fluid

Hi,

I want to model the presence of methanol droplets attached on the interior surface of the pipe in Simscape. In the simulation, water flow will be passed inside of the pipe to clean methanol droplets attached to the surface. This pipe is used for transferring methanol and before water flow is passing, methanol transfer is stopped and only methanol left is what is attached to the surface earlier.

The reason I am creating this model is I want to see what the best combination of pH, temperature and density of water is. Cleaning the pipe with the lowest amount of time and water is the result that I am seeking for.

I am not able to model methanol droplets on the pipe surface and also, I am not sure how to monitor level of methanol content left in the pipe after a certain amount of time passed or certain litres of water passed.

Thanks in Advance.

Anil

[Yifeng Tang]

This sounds very difficult to do in Simscape. I guess not only you need to track methanol and water in the pipe, you'll also need to model the air inside after methanol flow is stopped and before the water enters. Existing Simscape domains don't support multiple liquid species or mixture of liquid and air.

If, however, it's OK to simplify the problem as tracking a passive scalar (e.g. methonal concentration) in a pipe network FILLED with water, there may be a way to do it with some customization using Simscape language.

[Anil]

I think, I need help in this case as well. First, I have to start with simplified version of the problem and then adapt other aspects.

Can you please guide me in simplified version of the problem?

Answer 1

[Yifeng Tang]

It's possible to model a "solution", i.e. thermal liquid + passive scalar(s), using a quick-and-dirty way or a more formal one.

Quick & Dirty:

Use the existing TL domain. For components with internal states, like pipes and chambers, add a PS integrator block next to it to record the concentration or total mass/mol of the passive scalar inside the component. The input to the PS integrator is then the flow of the scalar into or out of the component. The scalar flow is going to be linked to the flow direction and the concentration upstream, so you'll need to be a bit care when putting the equations together in the PS domain.

I attached an example of a pipe I built on the fly using this method. The test case is to supply the pipe with flow of concentration of 0.5 from the left OR concentration of 1.0 from the right. Depending on the direction of the prescribed flow, the concentration in the pipe will gradually reach 0.5 or 1.0. Change the sign of the mass flow in the flow source to see the effect. The time constant will of course depend on the magnitude of the flow rate.

This is what's inside the pipe. All the sensors are there to make sure we take the right amount out and put the right amount into the pipe depending on the direction of the flow.

Now, the formal way of doing this: define a new Simscape physical domain based on the thermal liquid domain. If you feel comfortable about Simscape language, this is the way to go. You can get a taste of what this feels like by going through this documentation page:

https://www.mathworks.com/help/simscape/lang/define-a-new-physical-domain.html

and this on how to deploy custom component libraries.

https://www.mathworks.com/help/simscape/lang/building-custom-block-libraries-from-simscape-component-files.html

The first steps down this route are

1. make a copy of the whole thermal liquid domain.
2. change the name of the domain and references in all the blocks (things like "foundation.thermal_liquid.thermal_liquid"), so they are referring to the new custom domain you've just copied.
3. add a new across variable representing the concentration and a new through variable representing the scalar flow to the domain definition file, i.e. thermal_liquid.ssc or whatever you've renamed it to.

If you manage to finish these 3 steps and would like push further on this, please post the custom library you've built up to this step and I can guide you further.