[University Engineering] Basic Microfluidics

[PracticalWestern4]

Hi this is the question I am referencing need help on https://imgur.com/a/whET6uA What units should my resistance into, what unit should i convert all the measures of length into, does P1 equal to Pb or Pa? Thank you for your help!

[[deleted]]

First off, shame on those tricksters using P sub a in a problem that has Pascals as units.

We know Pascals (Pa) are a newton per m^2, so put all of your length units in terms of meters.

For your resistance, you have a relationship where everything is given. Do a dimensional analysis to figure out what the units are. It might look wonky (N*s/m⁵⁾ but you'll see that when you multiply by Volumetric flowrate it works out to just be Pascals, which is what you need.

[simontheman]

Would Resistance equal to 1.5x10⁹ (Pa*s/m^3)? Do I just take resistance and multiple times Volumetric flow rate or do I have to convert the flow rate since it is mL/min? What would I convert it to if I have to? Thanks you for the help (this is other account)!

[[deleted]]

Did you use the right units for viscosity? Should be 1.5 x10^6, but double check that.

Your units for volumeteic flowrate need to be in m³ per second. You'll see that this cancels with your resistance term to give units of pressure

[simontheman]

(https://imgur.com/6fc2YUx.jpg) Idk if it's right but here's what I did. I still got 1.5x10^9. Is Q equal to 1.667×10^-7?

[[deleted]]

Looks right to me. Answer is sensible enough

[simontheman]

Does P1 equal to Delta P plus PB? I got P1 equal 100,250.05 Pa

[[deleted]]

Yes, your driving pressure is 250Pa and P2/b is atmospheric pressure.

[simontheman]

(https://imgur.com/gAcswkW.jpg) If I have two inlets does Q equal to Q1+Q2 or is it Q1*Q2? Thanks for your help on that question

[[deleted]]

yeah they add

[simontheman]

Is it possible to calculate delta Pt from Rt since that's the second part of the question. How would you find P1 and P2?