Orifice (TL) temperature-dependent parameterization

Hello together,

I would like to specify an oil filter in Simscape. At the moment, I use the TL-Library orifice component for this task. I have test data available to specify the volumetric flow rate depending on the fluid temperature and the pressure drop. Unfortunately, I can't find any option to make the orifice behave temperature-dependent. There is only an option to parameterize the volumetric flow rate vs. the pressure drop. If I do so, the model behaves the same for each temperature.

Does anybody know how I could model this component in an accurate way?

Thank you!

Answer 1

[Yifeng Tang]

I can see two ways to move forward. One relies nearly solely on test data and the other incorporating more physical insights but also more work.

The first approach.

Assume you have a way to generate a table for pressure drop as function of temperature and flow rate: dP(mdot,T). You can use a 2D lookup table and a pressure source to enforce the pressure-flow relationship. Something like the part in the shaded area below:

This should work fine for the range where you have data for, but may not extrapolate physically.

The 2nd approach

Start with examine you data and see if you can collapse data from different temperature and flow rate onto one Reynolds number vs friction coefficent curve. If so, the Pipe block from the Simscape Fluids library allows such information as input and will provide more physically meaningful prediction.

[Emil]

Thank you very much for the answer.

I have one more question for my understanding: Components like an orifice are highly dependent on the fluid temperature because of its impact on the fluid viscosity in terms of pressure drop estimation. Do you know why this dependency is neglected in the orifice component? Was it to simplify the model or is there a deeper meaning behind it?

[Yifeng Tang]

The impact of the viscosity is NOT neglected, but it may appear to be small for the Reynolds number you are encountering. In the governing equation for flow vs deltaP (below), the term is calculated based on the viscosity at the average condition of port A & B.

If your is small and the term dominates in the denominator, becomes approximately proportional to and inversely proportional to the viscosity, typical for laminar flow. When is large and overpowers , becomes approximately proportional to , typical for turbulent flow, where viscosity shouldn't matter much, except for the Reynolds number calculation.

Hope this makes sense.

[Emil]

Yes, that makes sense to me. Thank you again for the quick answer.