How do you figure out volumetric flowrate of water through a pipe based on pressure and area?

Answer 1

you need to employ th ebournoulli equation and the fanninf (or darcy ) friction factor equation ...

The Darcy-Weisbach Equation for pressure loss due to friction (in the SI metric system) is:

ΔP = 4f(L/D)(ρ v2)/(2 gc)

where:
ΔP = pressure loss in Pascals
f = Fanning friction factor (dimensionless) from Moody's diagram
L = pipe length in meters
D = pipe diameter in meters
ρ = fluid density in kilograms per cubic meter
v = fluid velocity in meters per second
gc = gravitational conversion constant = 1 (kg-m)/(N-s2) in the SI metric system

And for head loss due to friction, the equation is:

Δh = f(L/D)(v2)/(2 g)

where:
Δh = head loss in meters
f = friction factor (dimensionless)
L = pipe length in meters
D = pipe diameter in meters
v = fluid velocity in meters per second
g = local gravitational acceleration of 9.807 m/s2

Answer 2

You will need a liquid flowmeter. There are several types available in the market.
One type of flowmeter looks like the blades on a ceiling fan with a ring around it. On the outside of the ring there are contact disks spaced every so often.
This works on the principle that as the liquid flows through the pipe it forces the blades and the wheel to turn. As the blades turn so does the contact disks. These disks then pass a sensor counter which counts how many times the disks pass. The faster the flowrate the faster the the contacts pass the counter and the greater number of counts, this is called flow proportional.
The flowmeter must be calibrated before using. This is done by running a determined amount of liquid going through the pipe and determining the number of counts for that specific volume.
If you run 1,000 gallons of liquid and got 1,000 clicks then your meter reads 1 gallon per click. This meter will have a factor of 1.0
meter factors will vary from .8 to 1.2
Area has nothing to do with meters. Volume does.
Pressure has negligible effect on meters since liquids are already compressed.
Temperature will have a significant effect on the volume measured and therefore must be corrected. F=0.00036
Hope this will help.

Answer 3

Volumetric flowrate = Velocity pressure x Area(cross section)

Answer 4

Here's an on-line calculator:

http://www.connel.com/freeware/flowcalc1.shtml

I checked it at 10 gpm in 100 feet of 3/4" steel pipe and it seemed to work fine (answer = 9.8 psi pressure drop).

A really handy rule of thunb is that in a lot of piping systems, water travels at 5 feet per second. It works as a rough approximation for garden hoses, fire hydrants, running streams, etc. It is very good for selecting pipe sizes. Slower than 5 fps and you bought too much pipe. Faster than 5 fps, and you'll need a much larger pump.

-David

Answer 5

You have to use an orifice plate inside the pipe line, between two flanges. The I D of the orifice and its flow coefficient is given by its maker. So you know the flow area.

Now you have to determine the difference of pressure upstream and down stream from the orifice plate at a distence specified by the maker of the orifice plate.

To measure the differential pressure between up stream and down stream points, you have to provode pipe taps in the pipe and insert pressure gages.

convert differential pressure into equivalent velocity. I think the formula is Diff Pr/density of the liquid times 2times g. and sqrt of the whole thing.

Vol flo rate= AXVXcoeff.

Check book on fluid dynamics.

Answer 6

Peter W's answer looks correct. Somehow the direct hot water is being heated in the boiler without it having anywhere to expand to. Its pressure will rise dramatically. You could get a mini expansion vessel fitted on the cold feed as close as possible to the boiler, however I would consult Worcester for advice first in case the boiler has its own backflow prevention devices. I don't think Nosda realises that you are referring to the pressure guage associated with the mains water pressure reducing valve rather than the heating pressure guage on the boiler.

Answer 7

Check out this link.