General > General Technical Chat
Bullshit units of measure
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rsjsouza:
Strictly to the topic of the thread, the bullshit is the motivation for the topic itself.  :box:

To the discussion about Dyson, I echo other comments here regarding durability: having used one for about 14 years I found out its maintenance was not bad at all, with the occasional hair cleanup of the brush and the chamber filters. It was sold just because the missus wanted one with a HEPA filter.

We also are on our second battery powered unit (the first one broke on a stupid accident after 10 years) and both work really well.

Regarding the robotic stuff, I got very tired of having to unclog/clean the brushes and the dust compartment four or five times at every cleanup. It might work for a house with a single person but, when you have three long-haired girls, it is quite impractical.
Berni:
Id say Air Watts are a good name because you don't want to confuse it with electrical Watts.

Vacuum cleaners have had a watts number all over the box for a very long time, but this number was the watts of electrical input energy and it was obviously much larger. You wouldn't want costumers confusing the two since the electrical watts is a significantly bigger number.

It is also perfectly possible that back then some manufacturers made less efficient motors on purpose just to get the watts number up. These motors have a ton of airflow trough them and i remember some vacuum cleaners blowing outright hot air out of them.
TheNewLab:
OK This on e really hurts, I hit my head on the chair laughing. no acro for that is there.

--- Quote from: boB on October 16, 2022, 02:24:04 am ---There is power in the wind...

For wind turbine use, the equation is,   Power (W) = 0.6 x Cp x N x A x V^3

--- End quote ---

Read https://tajhizkala.ir/doc/ASTM/ASTM%20F558__13.pdf  still does not really inform say 95% of potential buyers..Why not something simple like PSI? or what HVAC techs use in testing vent draw and volume?  I know Dyson makes great products, but "Air Watts" is. well, I read that entire PDF quickly and it is way more than I want to know. give me PSI and I understand right away
Berni:
Problem is that fans/pumps have characteristic curves that can vary in shape a lot.

It is easy to make a pump that makes a lot of pressure at low flow rate (this is a fridge compresor) and it is easy to make a pump that moves a lot of volume at very low pressure (this is a desk fan). Both of these beat a vacuum cleaner at pressure or volume. But what makes a vacuum cleaner a vacuum cleaner is that it can create a lot of pressure while simultaneously moving a lot of volume.

Since air watts are pressure and volume multiplied together means that both of them have to be a large number for the result to be a large number. So it is actually a very smart way to measure the performance.
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