Talk:Airwatt

Untitled

I added a bit to explain that airwatts are more direct measurements of vaccuum system power than electrical draw, because the system has inefficiencies which vary.67.184.72.52 (talk) 22:28, 18 August 2008 (UTC)

Formula

There were a few paragraphs in the formula section that referenced charts that were not in the article. The paragraphs were copied over from the Vacuum Cleaner article. I checked the history of that article and found that the charts referred to were not present and never were. It looks as if these paragraphs were copied from another source, word for word, without changing them to reflect that there were no charts with which to refer. There was also no source listed so the charts could not be added. As these paragraphs depended heavily on the charts (and make no sense without them), they have been removed. If the paragraphs are added back in, references to the charts should be removed and the explanation should be changed to not depend on them. Also, it should be moved out of the Formula section. — Preceding unsigned comment added by 72.21.246.99 (talk) 13:01, 2 November 2011 (UTC)

Nonsensical Unit

There is only one true unit of power and that is the watt defined as one joule per second. (1 W = 1 J/s). This airwatt BS is typical of USC units in that it was created to be deceptive and is proved to be in the article when each manufacturer is shown to have their own formula.

Even the so-called metric versions of the formula are wrong.

There is only one true formula and what is in the article is definitely not it. True power equals pressure times flow, with no fudge factors. In units that is Power in watts equals flow in cubic metres per second times pressure in pascals (1 W = 1 Pa.m^3/s).

Of course the power is also equal to the voltage times the current and since the voltage times the current will always be larger than the flow times the pressure, the difference is loss of power due to friction and windage in the motor or to put it in reverse, the ratio of the power used to produce the flow and pressure divided by the power due to the voltage and current is the efficiency. — Preceding unsigned comment added by Ametrica (talk • contribs) 14:25, 29 November 2014 (UTC)

I cleaned up an "alternative measurement formula" using the math tags, which I have not explored before. It looks much better this way! I did not change the actual math, of course.

I do have a question about a formula: $1{\frac {m^{3}}{s}}\cdot 1{\frac {N}{m^{2}}}=1{\frac {N\cdot m}{s}}=1{\frac {J}{s}}=1W$ which was changed to: $1~\mathrm {m} ^{3}\cdot \mathrm {s} ^{-1}\cdot 1~\mathrm {N} \cdot \mathrm {m} ^{-2}=1~\mathrm {N} \cdot \mathrm {m} \cdot \mathrm {s} ^{-1}=1~\mathrm {J} \cdot \mathrm {s} ^{-1}=1~\mathrm {W}$

I don't know why we would ever use seconds to a negative power to denote "per second," I find that very confusing and unhelpful. I didn't want to just change it back in case there's a reason I'm missing though. Mwenechanga (talk) 18:18, 15 December 2014 (UTC)

The same reason you would use a negative power with any other unit; it's standard notation, certainly for SI units. For compound units, the negative powers are much clearer than multiple slashes, and they make the dimensional analysis more straightforward (so the dimension is T^-1, or units of reciprocal time). By contrast, a unit would never normally be written as a vertical fraction of symbols, like it was before. I think it's also less cluttered to have the symbols on one line. Archon 2488 (talk) 20:03, 15 December 2014 (UTC)

I'll admit to being educated in the USA, so my experience with SI is more theoretical than actual, but my speedometer says km/h not km*h^-1. I'm not questioning the correctness of your math, just the readability: fractions are more accessible to those with a high-school education than negative powers. Mwenechanga (talk) 21:22, 15 December 2014 (UTC)

On the Wikipedia, SI-ness trumps readability every time. ---Wtshymanski (talk) 21:42, 15 December 2014 (UTC)

I don't think that's totally fair. Part of the rationale for having the SI standard is so that unit symbols are presented in a consistent way, which aims to increase readability. I've rarely if ever seen someone in the real world write units in the style of km/h or km⁄h; it's normally km/h or occasionally km·h^-1. But in the case of several compound units, the notation with the negative exponents is usually preferable. Archon 2488 (talk) 22:06, 15 December 2014 (UTC)

Transient Power Rating

I noticed recently that manufacturers of Shop Vacs rate their machines as having "Peak HP". This rating is often much greater than the nominal HP of the motor. One source says that this is simply the nominal voltage multiplied by the rated starting amperage of the motor.This is a transient power mostly consumed by accelerating the rotor and impeller. (Good thing they don't rate them based on the rated LRA (locked rotor amperage) !)

At first I thought this was related to the capacity of the tank. I thought about gas pressure vessels or hydro-pneumatic tanks. That is, the energy stored in the compressed gas adds to the power of the compressor when the valve is opened. This would be not be a steady state rating but a transient power. Vacuum tanks work in a similar fashion. The early power (vacuum assisted) automobile brakes had some reserve volume in the diaphragm chamber. The "hide away " headlights on some cars back then also had vacuum tanks to provide extra power to open or close the "cool" covers. These tanks reduced the load on the manifold vacuum "power". They would be of no assistance, however on the ancient vacuum powered windshield wipers - almost useless in Northern Winters!

I wonder is it worth the time to search for references discussing the relationship of the volume of the "suction chamber" to an equivalent boost in transient air wattage. In other words if by closing the orifice and allowing the tank to rise to maximum static vacuum (suction) "pressure" and then opening the valve quickly does this provide a little extra sustained air velocity at the nozzle? More precisely maintaining maximum velocity for a longer time before the suction pressure on the fan drops off with increasing flow. Or in a practical sense forcing the nozzle tight to the carpet, for example, then releasing it quickly provide maximum capture velocity longer. The larger the tank, the greater time for the increased velocity at the nozzle. The ratings would then show Steady state air wattage AND maximum air wattage for a sustained period of time. Aw(max) X time = Max reserved energy (Joules). The larger the tank, the larger the related MRE.

Pete318 (talk) 14:40, 17 January 2018 (UTC)

Why is there an "Alternative measurement formula"?

The two formulas are identical except for the coefficients, which differ by less than 0.25%, which is insignificant given the errors in the other factors? We could simply add a note regarding the two coefficients in use (and that they produce the same results to within a fraction of a percent.) The article makes it look like there are different formulas yielding significantly different results. 107.15.255.226 (talk) 21:09, 8 February 2021 (UTC)

I agree, and it's even worse than that: the alternative formula is already present in the definition section as well as in the alternative measurement section, making it look like 3 total formulas when in fact they are all basically the same. I think we can merge the additional info from this section into Definition and get rid of the redundancies. Mwenechanga (talk) 19:44, 10 June 2021 (UTC)

Article doesn't answer...

When a manufacturer quotes 'airwatts' do they multiply the maximum pressure (at zero flow) by the maximum flow (at zero pressure) to make the biggest number possible? Or do they calculate it by trying a bunch of points on the operating curve and quoting the maximum? — Preceding unsigned comment added by 87.81.41.128 (talk) 11:47, 21 April 2022 (UTC)