Talk:Orifice plate

Something seems wrong

The derivation of the orifice equation doesn't seem right somehow. I'll be back after I've had a chance to research it. Meanwhile, I cleaned up the math equations quite a bit (without changing them) and did some other very minor fixes in the text body of the article. - mbeychok 02:42, 1 May 2006 (UTC)

This comment is nearly six years old and pertains to the version here:

http://en.wikipedia.org/w/index.php?title=Orifice_plate&oldid=50986192

I suggest further discussion be placed in a new thread. - Ac44ck (talk) 06:08, 29 January 2012 (UTC)

Yes I noticed that as well. Can't do any substantial cleanup while at work, but if someone could go through that would be appeciated. The left side of the equation remains unchanged, but the right side is modified by introducing non-unity factors such as C_d. —The preceding unsigned comment was added by 24.73.96.170 (talk) 14:02, 3 January 2007 (UTC).

After the sentence "Introducing the beta factor (...) as well as the coefficient of discharge Cd.", the equation's right side has been multiplied with the factor Cd, but not the left side. As I understand arithmetic, this step better be reviewed. 145.253.165.178 (talk) 08:56, 11 August 2011 (UTC)

Formula (1) cannot be right. beta is d2/d1, thus if the orifice is significantly smaller than the pipe than beta << 1, beta^4 will then be even smaller and 1 minus a-ver-small-number is just one. In other words, the smaller the orifice is (compared to the pipe) the less of an influence it has on the gas flow!--12.176.38.188 (talk) 23:26, 27 January 2012 (UTC)

Note that the flow is based on A2, which gets smaller as d2 gets smaller. At small values of d2, the available flow area is much more important than the ratio of the diameters. I don't see that there is a problem at small values of beta. - Ac44ck (talk) 08:37, 28 January 2012 (UTC)

In looking further at this section, two other problems seem to be:

1. The introductory paragraph says the derivation is for laminar flow. This is not a requirement for the application of Bernoulli's equation.
2. P2 is said to be the "fluid downstream pressure." But in this application of Bernoulli's equation, P2 appears to be the fluid pressure in the plane of the orifice.

The orifice plate formula in this article is an adaptation of the formula for a Venturi meter, where a pressure tap does exist in a plane of maximum fluid velocity. The formula below the line "Solving for Q:" in this article is the same as the last formula in this section: Venturi effect#Flow_rate. - Ac44ck (talk) 01:07, 29 January 2012 (UTC)

Q: The derivation has to be wrong as Bernoulli requires all values to be at the same location, so you can't use the orifice area and then take the downstream pressure. In fact, if it is no viscosity then there is no net pressure drop. As others have mentioned, this is the formula for a venture, which is something else entirely. 204.85.24.5 (talk) 16:31, 22 May 2014 (UTC)Engineering faculty

Complete re-write and expansion

I have just completed re-writing this article and I believe it now a better article. I still intend to add a section on gas flows through orifices in the next few days. - mbeychok 22:53, 2 May 2006 (UTC)

Looks very good, Mbeychok. I just have one suggestion, to shorten the lead section per WP:LAYOUT#Lead_section. The equations would probably work better in their own section. Coming into the article cold, I'm used to a general lead section with details in later sections. Spalding 03:20, 15 July 2006 (UTC)

Done. Thanks for the suggestion. - mbeychok 04:25, 15 July 2006 (UTC)

Losses in orifice plate

Thank you for your useful article on the pressure drop across an orifice plate. It would be useful if you could add a section on the losses that occur across the orifice plate. It is frequently necessary to know the losses in a system and in some instances - such as in the outlet to a variable declining rate water filter - an orifice plate is used to increase the losses to prevent excessive flow. 217.15.119.158 13:40, 5 December 2006 (UTC)

Perhaps I don't understand your question, but Equation 2 in the article relates the mass flow to the pressure drop (P₁ - P₂) across the orifice for a liquid. By a simple re-arrangement of that equation, you could easily solve for the pressure drop, which is the pressure loss across the orifice, is it not? - mbeychok 19:28, 5 December 2006 (UTC)

Thank you for your response. The pressure change in Formula 2 is due to the change in velocity in the orifice arising from the the Bernouilli Equation. If you measure the pressure downstream of the vena contracta the pressure will recover but not to the same value as the upstream pressure because of energy losses in the device. It is these losses that I would like to be able to quantify. 217.15.119.158 11:26, 6 December 2006 (UTC)

I apologise for mis-understanding your question. I don't have one at hand, but any good textbook on fluid dynamics or fluid flow should have that information for you. - mbeychok 16:57, 6 December 2006 (UTC)

Reason for deleting external link added by Loughmsa

These are the reasons why I deleted the external link to a "Simple orifice flow calculation":

• The equation in that link is only good for air and only for one specific air density (which means only for one specific temperature and pressure).

• It is only good for the use of USA customary units, and we are now pretty much the only nation still using those units. The Wikipedia has a very large non-USA readership.

Basically, the linked calculation method was too limited and too simple for an article that is intended to explain orifice flow equations for use with any gas or any liquid. - mbeychok 01:46, 23 January 2007 (UTC)

external link not working

Flow through a sharp-edged orifice external link is not working please remove the same if it does not work for more. 59.180.94.55 10:49, 23 January 2007 (UTC)

I fixed that link and it now works. It requires that Shockwave be installed and it did that automatically ... for me at least. - mbeychok 17:05, 23 January 2007 (UTC)

Calculation of coefficient of discharge from Reynolds' number?

The article says that the coefficient of discharge can be calculated from the Reynolds' number (source given is Perry). If someone knows how to calculate it, or has a copy of Perry to hand, I would be very grateful if they would add this information to the article (I have googled extensively in vain). Cheers, 84.12.252.210 15:49, 4 July 2007 (UTC)

Orifice pressure for viscous fluids

If anyone would like to fill in orifice pressures for viscous fluids... after all, most of them are, and it becomes pretty important at small radii... Would be really nice!!! Cheers Michi zh 17:49, 26 September 2007 (UTC)

Measures vs. allows measurement

What distinction was the object of the last edit (09:16, 8 October 2007)?

The previous version says that an orifice plate "measures the rate". It was changed to say that it "allows the measurement of the rate".

It raises the question: If the orifice plate only _allows_ the measurement to be made, then what actually _does_ the measuring?

It also raises the question: _How_ does it _allow_ the measurement?

Perhaps the point is that only people can measure? Or perhaps that a connected differential pressure meter does a measurement which is ultimately interpreted as a flow rate?

Maybe the point is that the orifice plate is but one component in a total system which reports a flow rate.

The revised form is wordier. Maybe it is necessary to expand the reader's vision beyond this one component.

To be consistent, the next sentence would seem to need tweaking as well: "It uses ... Bernoulli's principle". Actually, the orifice plate itself doesn't do this -- a person interpreting a delta_P reading might Bernoulli's principle. More likely, they would use a precalculated chart.

Perhaps too much precision in language ultimately obscures the message by building a haystack around the needle?

I'm not suggesting undoing the last edit. I'm just trying to understand why the wording was changed and to explore how much anthropomorphizing is appropriate in technical writing. -- Ac44ck 16:01, 8 October 2007 (UTC)

I completely agree with you. So I changed the wording again to avoid the excessive precision in the language. - mbeychok 17:31, 8 October 2007 (UTC)

Re: edit at 01:09, 19 June 2008 by Gastester — "a device that is used to measure" seemed clear enough to me. One might say that a magnifying glass can be used to "facilitate measuring" of distances, but a yard stick still qualifies as a "a device that is used to measure" distances. -Ac44ck (talk) 07:37, 22 June 2008 (UTC)

Redundancy is in the eye of the beholder

Good catch, mbeychok, on the squaring of the Cd term in the formula for permanent pressure drop.

As to whether the last equality is "needed", I would argue:

First:

It could be handy to have an alternate, equivalent form readily available when a deadline is looming.

The cost of having this additional information available is practically zero. The cost of botching a hurried transformation of the equation (by overlooking the need to square a factor) may more significant.

That is why I rearranged the pressure drop equation when I created this section of the article: to have the equivalent form readily available. Unhappily, I overlooked the need to square a factor when doing so -- and the mistake survived for months in a document which is subject to public scrutiny.

Second:

(Q/A1) = V1 = constant regardless of bore diameter if the flow rate and pipe size are known.

(Q/A2) = V2 varies with bore diameter and is generally of less interest to me.

I like to be able to see formulae which are more directly related to V1, as the last equality is.

Third:

The last equality can be handy in situations where the bore diameter is to be determined based on the desired pressure drop, known pipe size and flow rate.

Using the last equality, one can iterate for beta without caring about or having to keep track of a tentative bore diameter during the process.

--Ac44ck 22:07, 17 October 2007 (UTC)

Ac44ck, I would very much like to respond to your above comment ... but I must leave in a minute for a very important meeting. Please bear with me and I will respond when I return in about 4-5 hours. Thanks and best regards, - mbeychok 22:40, 17 October 2007 (UTC)

Ac44ck, thanks for waiting. I could easily check your first equality and find it to be correct except for the lack of squaring the Cd term.

However,I could not do the same with the second equality. Not only did it have the same lack of squaring the Cd term, I simply don't see how that second equality of yours ended up with a $\beta ^{4}$ in the denominator. That made me worry enough to ask myself, do we we really need it?

If you would correct the Cd squared errors in both equalities as well as explain to me how $\beta ^{4}$ ended up in the denominator of the second equality, then I would have no objection retaining your second equality. Again, best regards. - mbeychok 03:15, 18 October 2007 (UTC)

mbeychok, thanks for the further reply after your long meeting.

The transformation seemed a bit tricky to me. Perhaps it wouldn't have been so tricky (mumble) years ago in college, but transforming equations isn't something that I do every day now and I didn't want to lose the effort under a pile of papers. So I added the second equality to the article -- where someone else is doing the archiving, etc.

The denominator of the first equality contains the factor A₂².

The square-root of that factor can be rewritten as follows:

A₂ = A₁ * (A₂ / A₁) = A₁ * (d₂ / d₁)²

But: $\beta$ = d₂ / d₁

So: A₂ = A₁ * $\beta$²

And:

A₂² = A₁² * $\beta$⁴

So the transformation to the second equality replaces A₂² in the denominator with A₁² * $\beta$⁴.

I considered dividing through by $\beta$⁴ -- changing the factor in the numerator to (1/$\beta$⁴ - 1) -- so there would be only one instance of $\beta$ in the second equality. I might write it that way in a spreadsheet formula, but it seemed better to avoid stacking fractions in the printable form.

Thanks for finding that the Cd factor wasn't squared.

Best regards --Ac44ck 04:56, 18 October 2007 (UTC)

I am happy that we were able to settle this amicably. In an earlier response you said ... and the mistake survived for months in a document which is subject to public scrutiny. I assume that you have now corrected that document as well. Again, with best regards, Milt Beychok. -- mbeychok 05:16, 18 October 2007 (UTC)

formulae expansion factor

The formulae, stated for the expansion factor is used with nozzles and venturis, according to perry's handbook. The formulae for Y for orifices is different :

Y = 1 - [(1-r)/k](0.41+0.35Beta^4)

Comment plz. —Preceding unsigned comment added by 195.73.116.62 (talk) 10:08, 5 March 2008 (UTC)

I found the same mistake in the formula. The two formula gives quite different results. Using the current formula Y=0.20 and using the above formula, Y=0.71. Pls correct the formula in the article —Preceding unsigned comment added by 203.199.60.145 (talk) 04:58, 13 May 2008 (UTC)

This is the eqn that is currently on the page (11/14/13): Y = 1 - [(1-r)/k](0.41+0.35Beta^4). Can someone verify if this is correct? Did the above two comments get addressed?Ad000000 (talk) 17:30, 14 November 2013 (UTC)

Possible expansion

I could expand this article in a few areas:

- Standards: ISO-5167 and AGA-3
- Equations from the above (copyright?)
- More detailed diagram showing streamlines and pressure distribution
- Deflection of orifice plates
- Construction of pressure tappings (flange, corner, d and d/2)
- Use of orifices for high-accuracy applications (no, honest!)
- Construction of orifice plates

Some or all of this may be considered more detail than necessary! Any opinions? Mike.seabrook (talk) 16:38, 16 October 2008 (UTC)

A supplementary diagram could be interesting. I don't know that I would replace the existing one, as it seems to provide enough detail to apply the formulae. I am reminded of CAD templates from manufacturers. They often provide a single template, which shows more detail than necessary on a floor plan. But that level of detail, and more, may be wanted in a maintenance manual.

The existing lead image seems adequate to me, though I am surprised to find that no higher resolution is available by clicking on the image. A diagram showing streamlines and pressure distribution would be helpful in a section of the article which touches on those topics. -Ac44ck (talk) 19:11, 16 October 2008 (UTC)

Mike, when I created this article, it was my intent to present the derivations and final equations for predicting the flow through orifice. It was not my intent to get into the detail that an orifice manufacturer or a maintenance manual might provide. I have no objection to adding some additional material as long as it doesn't get into so much detail the main thrust of the article is lost. Regards, mbeychok (talk) 23:36, 16 October 2008 (UTC)

Non-choked flow equation

Is the applicability of the non-choked flow equation to real gases overstated somewhat?

Equation 2 seems to be exact for real gases.

The text beneath the "Flow of gases through an orifice" heading mentions that the first equation for Y is for ideal gases. Equation 3 is an approximation of Y for usual values of $\beta$.

As equation 4 seems to rely on equation 3, wouldn't equation 4 be for an ideal gas?

Equation 5 restores some reality to the situation by introducing the compressibility factor, but I'm not sure that it eradicates the approximation of ideal gas behavior in equation 3. -Ac44ck (talk) 22:52, 7 November 2008 (UTC)

Middle dots to separate units

I find that the removal of middle dots to satisfy an unreferenced "SI convention" creates ambiguity in the text.

Removal of the middle dots is contrary to MOS:NUM#Conventions:

When units are combined by multiplication, use a middle dot (·) to separate the symbols. For example ms is the symbol for a millisecond, while m·s is a metre-second.

The change from "kg/(m ·s²)" to "kg/(ms²)" raises the question: "Is that kilograms per millisecond squared?" Perhaps it should be "obvious", but it may not be.

The discussion here http://www.unc.edu/~rowlett/units/symbol.html also suggests using a dot and says "symbols should not be placed next to one another with nothing between them." -Ac44ck (talk) 19:28, 26 December 2008 (UTC)

Clarify Picture and Equations

The picture in top right corner may mislead readers. Text states that P2 is the downstream pressure, however, it might be clearer to say P2 is the pressure at the orifice diameter or at the vena contracta. Or did you mean to say something else? —Preceding unsigned comment added by 64.89.118.226 (talk) 21:23, 14 August 2009 (UTC)

The picture doesn't show P2. I don't understand how the picture is misleading concerning P2.

The pressure at the orifice diameter exceeds the downstream pressure in sonic flow.

It seems to me that neither the picture nor the text need fixing regarding P2 -- except the mis-statement about it being the pressure "in the orifice hole" beneath equation 6, which I will now fix. - Ac44ck (talk) 02:25, 15 August 2009 (UTC)

Gas massflow calculation in error

The calculated massflow for a given orifice and given pressure drop is about a factor 4 too small. This statement is based on : - reality check with real orifices in real applications where the flow is measured by calibrated flow transmitters (error approx 1%). - comparison with the results by CONVAL ver 8.0 (engineering software package).

168.88.70.34 (talk) 12:17, 1 February 2011 (UTC)

I checked out one of the references for the equation "Flow of gases through an orifice", from Perry's Chemical Engineers Handbook 8th ed, you can get a preview of the necessary page (pp996) on Amazon.com. That equation (10-22) mentions "g" (the graviational acceleration constant) inside the square root. Could this be contributing to the discrepancy? --RedHotIceCube (talk) 17:13, 3 February 2011 (UTC)

Where should Cd be introduced

This is a useful derivation to have in the Wiki, and it is mathematically correct. However, I find it conceptually unclear where Cd is introduced without explanation. It simply adjusts the flow term. This is done after the continuity equation is utilized, so a reader might conclude that the mass balance has to be adjusted using Cd. in fact, the mass balance cannot be violated. Cd accounts for frictional losses in the original energy balance. It would be better, therefore, to introduce it in the energy balance. I would suggest that, after the first equation is presented with "negligible friction losses" that it then be presented with the final term multiplied by 1/Cd^2 to include the friction loss. Carrying this term through will then give the 7th current equation where Cd is introduced in the present version. I am new to this and do not know how to edit the entry itself, so I'm only participating with a talk entry. Skdentel (talk) 14:23, 22 September 2011 (UTC)Steve Dentel

Is practice different from theory?

Here is an equation for volumetric flow calculation for an orifice plate flow meter found in an app note of an instrumentation manufacturer emerson. I think it is intended for use with various grades of natural gas.

Qv = 218.527*Cd*Ev*Y1*(d^2)*[Tb/Pb]*[(Pf1*Zb*hw)/(Gr*Zf1*Tf)]^0.5

Where

Cd = Orifice plate coefficient of discharge

d = Orifice plate bore diameter calculated at flowing temperature (Tf) - in.

Gr = Real gas relative density (specify gravity)

hw = Orifice differential pressure in inches of water at 60 degF

Ev = Velocity of approach factor

Pb = Base pressure - psia

Pf1 = Flowing pressure (upstream tap - psia

Qv = Standard volume flow rate - SCF/hr.

Tb = Base temperature - degR

Tf = Flowing temperature - degR

Y1 = Expansion factor (downstream tap)

Zb = Compressibility at base conditions (Pb,Tb)

Zf1 = Compressibility (upstream flowing conditions - Pf1, Tf)

It seems to be saying that the volumetric flow rate Qv is proportion to the square root of the differential pressure (hw) multiplied by some other factors. It does not seem to be evenly remotely equivalent to the equation given in the article. (Why don't they ennumerate the equations in Wikipedia articles?) Why is there so much discrepancy? (Entropy7 (talk) 23:32, 17 January 2012 (UTC))

Flow Measurement Engineering Handbook by Richard Miller I think is considered by many people to be more authoritative than Perry on the the subject of orifice plate flowmeters. Perhaps it would help to make this book the principle reference of the article.(Entropy7 (talk) 16:57, 20 January 2012 (UTC))

Closed: Equation 8 not correct?

Equation 8, and the previous equations from which it was derived, do not seem correct. Looking at the expression within the square brackets inside the square root, as P1 becomes larger, the value of the square bracket decreases. This gives a lower volume flow rate. It is self evident that increasing upstream pressure must also increase volume flow rate through the oriface plate. In some of the related equations it will be an increase in mass flow rate.

Another problem with Equation 8: In the nomenclature M is described as Molecular Mass (also known as molecular weight). However, the units shown are for Molar Mass, not Molecular Mass and I suspect that Molar Mass is correct.

Bicyclehub (talk) 22:02, 30 July 2012 (UTC)

Closed: Equation 8: Correct!

Having checked Equation 8 by using another method, it seems that it is in fact correct. The volume flow rate does increase at first, but then starts to reduce when p1 is approx. 100000Pa greater than p2 (in my equipment at least). This is counter intuitive. If you pull a tack out of a bicycle tyre you would expect more air to issue when the tyre is harder. The velocity at exit, on the other hand, does continue to increase as p1 increases. This is (I guess)why blowing harder on a trumpet makes a louder sound. And why a bicycle tyre hisses more noisily in the early stages of deflating.

Bicyclehub (talk) 08:25, 2 August 2012 (UTC)

Hard to fathom step in compressible flow derivation

What's going on here in the compressible flow section? It isn't clear at all. How has equation 4 been substituted into equation 3 to get the next line? The result looks OK, but it appears like the last equation has actually been derived by another route to that claimed in the surrounding text(in the bottom line, where has the Karman constant and beta gone from equation 4?)

$(3)\qquad {\dot {m}}=\rho _{1}\;Q=C\;Y\;A_{2}\;{\sqrt {2\;\rho _{1}\;(P_{1}-P_{2})}}$

$(4)\qquad Y=\;1-{\bigg (}{\frac {1-r}{k}}{\bigg )}{\bigg (}0.41+0.35\beta ^{4}{\bigg )}$

${\dot {m}}=C\;A_{2}\;{\sqrt {2\;\rho _{1}\;{\bigg (}{\frac {k}{k-1}}{\bigg )}{\bigg [}{\frac {(P_{2}/P_{1})^{2/k}-(P_{2}/P_{1})^{(k+1)/k}}{1-P_{2}/P_{1}}}{\bigg ]}(P_{1}-P_{2})}}$

JBel (talk) 07:29, 18 October 2013 (UTC)

Quite right. (4) is the empirical formula for Y, also found in ISO standards as ϵ (epsilon), for thin-edge orifice plates used for flow measurements with β in the range 0.2 to 0.75. The following formulae are for flow through orifices with smaller β and are not generally used for flow measurement. I'll try to make it less misleading but I may not succeed in making it clear. NebY (talk) 11:43, 18 October 2013 (UTC)

Flow coefficient error?

The article says the discharge coefficient Cd should be modified by the "velocity approach factor sqrt(1-beta^4), producing the "flow coefficient" C. The reference for this (1)no longer leads anywhere, and should be removed. Someone's lecture notes may be a dubious reference anyway! In section 6.2 of this fluid mechanics tutorial: http://www.freestudy.co.uk/fluid%20mechanics/t9203.pdf it shows an equation to account for the same inlet velocity phenomena, however if you dissect it a small bit you find that the above correction factor is actually sqrt[1-beta^4*(p2/p1)^2/k]. This is not insignificant in the result. If this is true, the page should be corrected, and and new reference added. Ad000000 (talk) 17:28, 14 November 2013 (UTC)

I agree that theoretical section seems to have been corrupted and could benefit from close analysis and rewriting. For various reasons, I'm more keen to bring the practical section up to scratch, leading up to the handful of equations normally featured in standards and practical handbooks. So if someone else would like to tackle the theory section.... NebY (talk) 18:41, 24 February 2014 (UTC)

Closed: Value and units for Universal Gas Constant R

Pertaining to Equations 6 asnd 8, should the value and units for R be 8314.5 J/kmol-K?184.71.62.254 (talk) 14:52, 17 December 2013 (UTC)

It could be. But why prefer a bigger number with a bigger unit? - Ac44ck (talk) 04:41, 18 December 2013 (UTC)

No, that would not be compatible with the other SI units. If your density calculations are out by a factor of a thousand, then I suggest checking that you are using the molar mass in kg/mol. Many handbooks provide the molecular weight instead, which must be multiplied by the appropriate molar mass constant of 0.001 kg/mol to give the molar mass in kg/mol. NebY (talk) 09:40, 18 December 2013 (UTC)

OK now I see the units of M are in kg/mol. I am so used to seeing them in g/mol or kg/kmol that I overlooked that. My error. Apologies.184.71.62.254 (talk) 14:46, 18 December 2013 (UTC)

Closed: Beta /B4 Factor

There is no explanation nor any links to other articles on what this is, nor how to calculate it, or even what it means. The equations and most of the article are very dependent on this variable but there is absolutely no explanation of where b4 comes from except "set it to a value between .2 and .6". That's not very helpful or explanatory. — Preceding unsigned comment added by 98.172.66.86 (talk) 14:48, 2 May 2014 (UTC)

Beta is explained Michi zh (talk) 14:27, 4 February 2017 (UTC)

Closed: Equation 2 seems incorrect density should be on denominator?

oops sorry my mistake I posted to the working page — Preceding unsigned comment added by 203.97.93.222 (talk) 21:38, 5 August 2015 (UTC)

The second equation concerns mass flow, which is higher - in a given orifice at a given differential pressure and so forth - for denser fluids. You may be thinking of volume flow; apply the preceding equation and you'll see that the volume is indeed lower with denser fluids, as you'd expect. NebY (talk) 21:41, 9 August 2015 (UTC)

References not working

Reference 13 and 17 not working. Please check. — Preceding unsigned comment added by 59.99.242.131 (talk) 01:35, 19 December 2015 (UTC)

Shouldnt a much more simple formula be added?

I came here trying to figure out about how much pressure drop I'd get across a small orifice at a given flow rate. The formula, to a precision of 1% is way shorter than one line. What's currently on here is really not very useful to me, and I think I'm not alone by far. I'll be adding a more simple formula for the special case of non-turbulent flow though an orifice which is smaller than 1/10th of the pipe, to a precision of about a few percent. Now my question is: Where should it go to? My suggestion is after the "pipe" section, and adding an "exact" to the title of the Computation section. Michi zh (talk) 14:56, 4 February 2017 (UTC)

OK now I think I understand more (0. Viscosity effects are negligible for gases, hence not part of the formula.)

1. The "Computation" section is a description of the ISO standard to compute this, precisely but elaborately.

2. The "Theory" section culminates in what I was looking for.

3. The symbols used in "Theory" and "Computation" are different.

My suggestions are as follows:

1. Description part: Add the "compressible flow" formula in "description" section, including commentary of the variables, i.e. that C is usually between 0.6 and 0.9ish.

2. Structure: Making "Computation" a separate section, hirarchically the same as "Application" and "Theory". Adding subsections for the different variables, and linking them in the "description" section, and calling it "Computation according to ISO 5167" to clarify the difference between theory and computation.

3. Aligning the differences in notation between "Computation" and "Theory".

I've gond and copy-pasted the article into my Sandbox and made these changes, which I've also submitted for review there like it were a new article. I hope this is not too far off wikipedia's best practice.Michi zh (talk) 18:53, 7 February 2017 (UTC)

Update: I've now transferred the changes into the article. Subchanges can still be traced in my Sandbox.Michi zh (talk) 09:52, 8 February 2017 (UTC)

Apliccability of compressible flow formulas.

Doing the math for a restrictor plate (30 micron hole in a 6mm tube), pulling 100mbars vacuum against atmospheric, the two formulas for compressible flow give different results by a factor of 3. If someone would pinpoint me to why this is (I'm guessing that its due to the limits of applicability for the ISO method, which is used to calculate epsilon and that the version without epsilon is correct for my case), I'd gladly do the research and detail it in the article. Michi zh (talk) 09:50, 8 February 2017 (UTC)

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Mistake in Theory - Incompressible flow

It starts from: $p_{1}-p_{2}={\frac {1}{2}}\cdot \rho \cdot V_{2}^{2}-{\frac {1}{2}}\cdot \rho \cdot V_{1}^{2}$ and $q_{v}=A_{1}\cdot V_{1}=A_{2}\cdot V_{2}$   but $p_{1}$ and $p_{2}$ stand for the pressure at a distance from the orifice. And so should $V_{1},V_{2},A_{1}$and $A_{2}$. Subscript 1 and 2 should each stand for a specific location. Yet $A_{2}$ is the section of the opening. BartYgor (talk) 08:14, 21 February 2018 (UTC)

False statement about absolute pressure ~ flow

The following sentence can not be correct. Neither the absolute pressure nor temperature have any relevance regarding flow. There might be no flow at all but still a high absolute pressure and/or temperature. It has to be a pressure differential across the orifice. Hence I remove this:

"Even compressible flows of gases that vary in pressure and temperature may be measured with acceptable uncertainty by merely taking the square roots of the absolute pressure and/or temperature, depending on the purpose of the measurement and the costs of ancillary instrumentation." --Eheran (talk) 06:52, 16 July 2019 (UTC)

Yes, measuring temperature and pressure's often a good substitute for measuring density, but you still need the pressure differential. 92.19.24.47 (talk) 13:00, 12 October 2019 (UTC)

Swedish version of the article

Noticed there's a swedish language article about the same thing which isn't linked in the "lanugages" part. I don't know how to link the different lanugage articles together so thought someone else on here might help.

The swedish article can be found here https://sv.wikipedia.org/wiki/Strypfl%C3%A4ns Not sure why they aren't connected already

Dux Ducis Hodiernus (talk) 13:40, 15 January 2020 (UTC)