Similarity between P&ID and Electrical diagrams ???

[mariolucas75]

Dear Forum Memebrs,

Could you please advise if it is possible to think that

in some instances the flow of fluid in P&ID diagram is similar to the flow of electrical current in circuit boards: in order to have an electric current you have to have a potential difference across two points (which is called voltage across two point s)thus defining potentials at each junction of complicated electrical circuit one can identify the flow of current, so much the same to have a fluid flow across two points you have to have a pressure differential...


Thanks

 

[waross]

That may be possible, but consider that if you have to bend the parameters in order to fit the analogy, there comes a point where the analogy may no longer be very useful.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[xnuke]

The analogy only holds for laminar flow, and like simple electric circuits, laminar fluid systems can be solved using linear equations. Once flow becomes turbulent - which most fluid systems are - the fluid system behaves nonlinearly, and iterative solvers must be used for solving.

xnuke
"Live and act within the limit of your knowledge and keep expanding it to the limit of your life." Ayn Rand, Atlas Shrugged.
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[zeusfaber]

Lots of people certainly do apply their knowledge of one type of system to help them get a feel for the other - especially using a simplistic understanding of fluid flow to help them get a start with electrical circuits. It only works to a point:

As soon as your electrical circuit starts to include capacitance and inductance, the corresponding fluid components stop being intuitively familiar things.

Any analogy will break down if pushed far enough (see both Bill and xnuke's posts above). If you already understand both systems well enough to be able to tell how far it's safe to push the analogy, you probably don't need it any more.

When it comes to applying electrical experience to fluid problems, people often come unstuck when they forget that most of their electrical experience is based on constant voltage systems, while lots of (though by no means all) fluid systems work at roughly constant flow.​

A.

 

[cswilson]

To build on the earlier comments:

I think these analogies are useful at the conceptual level, with matching fundamental concepts of potential and flow. MIT formalized these analogies into a discipline they call "Systems Analysis", which is where I learned of it, and I have found it very useful at the high level for general understanding. They even extend the analogy to mechanical and thermal systems, even magnetic!

But the warnings from the others above must be heeded when you get into the details, especially when systems deviate from mathematically linear behavior. Each type of system tends to deviate in its own special way, and if you rely on your intuition from one type of system, it is not likely to help in another.

Curt Wilson
Omron Delta Tau

 

[zappedagain]

This thread reminded me that I put together this system-view of electrical and mechanical equivalences early on in my career. Enjoy!

Z

 

[ScottyUK]

zeusfaber,

Inductance - mass of the fluid? Capacitance - accumulator?

Agree that it can get harder to deal with the analogy than the real quantities!

 

[zeusfaber]

Inductance as density of the fluid? Makes the maths work reasonably well, but a complete head-scratcher for helping understanding of circuits as it's a property of the working fluid, rather than of the system components.

Capacitance as accumulator? That's an easier concept to wrap your head round, but you need to choose your accumulator with care (the ones that fit the maths are probably not the type most people see in everyday use).

A.