Calculate Pressure Differential

Use a formula that calculates pressure loss in a pipe line. There is plenty in the internet. Get accustomed to Reynolds number and Darcy Weissbach and so forth...

The easy way is how much pressure you get at the inlet minus the outlet pressure is your differential. But you knew this, right?

That 1/4" (6.4 mm) tube will not present much of a challenge at 10.4 m length. 16 L/hr is only 4.444 ml/s. 1 pascal-second = 1 newton-second per meter²

1 Pa·s = 1 N·s/m² from AquaCalc website:

http://www.aqua-calc.com/what-is/dynamic-viscosity/pascal-second

A 6.4 mm diameter tube has 3.216988 x10^-5 m² cross-sectional area (assuming your dimension represents the inside diameter, not the outside diameter.)

Now, Johnny, go do the rest of your homework, for I shall not do it for you.

You think we can give you an answer, but we need to be told 1000 litres=1m3?

Ask your tutor or classmates how to do it. It's quite straightforward. Then post your answer here and I'll tell you whether it's right.

Given data

L=10.4m

R=D/2=6.4/2=3.2mm=0.0032m

v=0.12Pa

Q=16lit/hr=16×0.00000028=4.48×10^-6 m3/s

P=??

according Poiseuille's law,

Q=(πPR^4)/8Lv

P=(4.48×10 ^-6×8×10.4×0.12)/(π×0.0032^4) =135.7kPa

Is this Answer is right??

Yes, that's right, well done!

But you didn't check that Poiseuille's formula applies, which is only for laminar flow. Should work out Reynold's no. It's more complicated for turbulent flow.

Just by the seat of my pants, I suspect the Reynolds number is really low on this one.

It is, but best to check. I doubt if the OP has as good an intuitive feel for these things as you.

Good job! So you can see it does not take much pressure to get this job done.

Use a valve and you won't have to calculate it.

Yes, use a long tapered valve, these are really easy to adjust to a good steady value.

VREL is what they are called, then add a small flow-meter and you are all set.

There are some tangents being gone off on there! It's more than likely a homework question, rather than wanting to do something practical. But if it's the latter more detail is required about what he's trying to do. For a start, if it's a pumped system he'd need to find the headloss in order to spec the pump. And he didn't say he wants to control the flow, by a valve or otherwise.

I can see this being a sample line to an online analysis instrument/transmitter, where the supply pressure is just static pressure of a storage tank (such as condensate in a power plant). Maybe the length of tubing relates to the tap off from the main condensate pipe that is over head. Since this information is not volunteered, it is just guesswork.

^{In this problem data is not use in practical. I just put questions from my stuff. I don't have any practical experience.}

OK thought so