Talk:Flow measurement
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--Mlloydmequon 17:29, 31 July 2006 (UTC)MikeIs this article a business directory listed at the bottom? is that policy?
- I have deleted the entire "Companies selling flow measurement devices" section. Wikipedia is not a Web directory, and this list is an open invitation for spammers. If there are any truly notable companies that are worth a mention, they will be notable enough to have their own Wikipedia article, and we can link to that. —Caesura(t) 12:23, 17 December 2005 (UTC)
31July06: The article is useful as it is. But it suffers a bit from its apparent perspective in potable water distribution. To wit: It omits several important classes of flowmeters:
1) Flowmeters providing visual flow information such as:
a. rotameters with poppets positioned by flow/gravity interaction b. totameters with poppets positioned by flow/spring interaction c. vane type flowmeters
2) Low cost "mechanical" flowmeters
a. paddlewheel flowmeters with pickups using reed switch or Hall effect or optical or ?? sensors b. turbine flowmeters with various pickups
3) Other flowmeter types:
a. Fluidic oscillation meters (related to vortex shedders, but different enough to justify their own mention) b. Target meters (related to pitot meters, but, again, different enough for mention).
4) Beyond this, venturi meters and orifice meters should be classified as "head flowmeters" or something similar. This would then be a reasonable place to include open channel flowmeters such as:
a. V-notch wiers b. Parshall flumes.
I'm sorry that my expertise is not up to the task of providing actual improved text for the Wiki entry. Hopefully, some expert will take my (probably still incomplete) list and use it to extend the entry.
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[edit] Is that density or viscosity of fluid will affect the flow
Dear all,
Is that anyone come across this issue before? How does the density or viscosity affect the total flow? for example, with different density of gases, will they have same quantities if their flow with same units (1000 m3/hr, etc)?
Regards, Lee
[edit] Venturi meters
Is it really enough to say that a venturi meter constricts flow 'in some fashion'? I believe a venturi flowmeter must use a venturi tube, just as a orifice plate meter must use an orifice of a very specific size in order to function.
[edit] Determining mass/flow rates etc
Hi
I need help on a formula that I can use in spreadsheet or database to calculate total quantity of fluid passed over a period of time.
Example pressure 25 psi, pipe bore 2 inches, length 12 feet, fluid = water time 20 minutes.
I would appreciate an answer from anyone who can spare the time please
Nb I would be using MS Excel or Access (sad I know but limited resources).
Thanks
Allan
[edit] Calculating flow rates (for Allan)
Unfortunately Allan, the calculation isn't as simple as your question implies.
The simplest equation for calculating flow looks like this:
V = Av
where:
(V) is the Volumetric flow rate (in your example, probably in cubic feet per minute [cfm])
(A) is the cross-sectional area of the pipe. In your example the area would be the pipe radius (half the diameter or 1 inch) squared times pi (3.14) or 3.14 square inches. For most flow equations in standard units, you will want the area of the pipe in square feet, which in this case would be 0.0218 square feet.
(v) is the average fluid velocity. This is where your example gets harder. The flowmeters in this article really only measure fluid velocity because the pipe size (and thus the cross-sectional area) is fixed by the meter itself. If you don't know the fluid velocity in your example, you can't calculate flow. If we could measure flow with the example information you provided, flowmeters would be unnecessary, you could measure flow with a pressure gauge and a tape measure.
However let's say you did know the velocity, and you didn't list it because you didn't know it was important. Lets say for example it's 20 feet per second (fps). The volumetric flowrate would be 0.0128 square feet times 20 feet per second or 0.256 cubic feet per second. Cubic feet per minute is a more standard unit of measure, so converted that would be 15.36 cfm.
There are 7.48 gallons in one cubic foot of water, so in gallons per minute (gpm), that is 15.36 times 7.48 or 114.9 gpm.
If it was mass flowrate that you wanted, the above equation is still necessary. The following equation is then applied:
m = Vρ
where:
(m) is mass flowrate
(V) is volumetric flowrate from above
(ρ) is the density of the fluid (in this case water)
Density of pure water is a function of temperature. If the temperature of the water in your example is constant and known, you could look up the density on a table. For now, we will use 62.3 pounds per cubic foot, which is the approximate density of water at 70°F.
Using the volumetric flowrate we calculated above, the mass flow rate would be 15.36 cfm times 62.3 pounds per cubic foot or 956.928 pounds per minute.
After you calculate the flowrate the rest is the easy part. Take the flowrate (we'll use the 114.9 gpm from above) and multiply it by the time that has passed to get total volume. From your example we will use 20 minutes times 114.9 gpm and we see that a total of 2298 gallons of water have passed through our 2 inch pipe in the 20 minutes alloted.
Although I'm sure this entry didn't get you closer to your spreadsheet equation, I hope it shed some light on flow calculation in general, as well as the variables required to calculate flow.
Brandon W.
[edit] Query for Instrumentation Engineers
How would an instrumentation engineer differentiate between the measurement of flow and pressure? Plz help —The preceding unsigned comment was added by 61.0.17.157 (talk) 02:00, 3 April 2007 (UTC).
