I haven't (and will not) invest any time doing the numbers but, a quick think about the Dyson fans leads me to conclude the whole thing is a big marketing scam. Kudos for pulling it off, but the thing ain't magic.

For starters, it has blades. It definitely has blades. They are simply concealed. It's like saying my computer has no fans when the fans are not visible from the outside. Nonsense.

Second, it takes a certain amount of power to accelerate a mass of air to a given speed. That does not change magically because the thing has a Dyson sticker on it. The most efficient way to accelerate a mass of air is, wait for it, a properly designed fan. It am pretty certain the Dyson contraption is actually much less efficient than a properly designed plain fan which produces the same airflow. It absolutely could not be more efficient, no way. Nowhere in conventional physics do you get more --of anything-- than you are entitled to.

In fact, the larger the fan the more efficiently it can accelerate a mass of air. Because the Dyson fans are constrained by the small space of the base they have to use screaming little fans to push against the back-pressure produced by the path the air has to follow.

Maybe not as sexy, but a really well designed fan with optimized airfoils and balanced rotor IS magical in the sense that it can be so much better than the stamped metal contraptions one usually finds at the store. I have seen fans like that come-up here and there but they are rare.

I did a project many years ago where we had to design and optimize an efficient cooling system for a 1500 Watt LED array. We ultimately ended-up going with a hybrid fluid/air system. However, for the bulk of the project we tried to make an air-only approach work because it was deemed simpler and easier to manufacture. I learned a lot from running tons and tons of FEA fluid and thermal simulations as making a number of prototypes. There is no free lunch (AKA: Conservation of Energy).

I haven't seen any checks on this, but I suspect the Dyson can probably move more air than a regular fan. It probably isn't more raw energy-efficient, but it can be more comfort energy-efficient (more comfort for the same energy), because their principle makes sense -- if you use a regular fan, you air speed is going to be dictated by the blade speed, while the amount of air depends on the area. With the dyson, they can get a much greater area, which dictates confort, with the same air speed, because they've distributed the stream along this circle, and it picks up more air as it goes (and loses speed).

My point is, it may be poorly executed, but in principle it sounds nice, not even taking into account you don't actually have an exposed blade to worry about. It's not a scam.

And I am arguing it is complete hogwash.

If a ring of air magically propels a lot more air around it, do you think a fan of the same diameter might just compel the same air molecules to follow suit?

> if you use a regular fan, you air speed is going to be dictated by the blade speed

On the Dyson air speed IS dictated by blade speed. They have a damn fan at the base pushing air through the system and they use that air to accelerate some more air around it. Again, I am not going to waste my time doing any math. My educated guess is that the efficiency, when compared to a properly designed fan of the same diameter is atrocious.

One other point, air speed coming out of a fan is not solely dependent on blade speed. Blade shape, diameter, angle of attack, duct length and even airfoil come into play.

You also have centrifugal, fans which operate under slightly different principles and can deliver airflow at greater pressure than axial fans.

More importantly, if you are trying to cool something air speed isn't always the most important criteria. The volume of air moved per unit time is extremely important. It has to be matched to the thermodynamics of the heat exchange that will happen with whatever it is you want to cool Delivering air faster and with greater volume than necessary is a waste of energy.

Lady who cuts my hair has a bunch of the dyson ring fans. She likes them because they're easier to clean and stylish.

My pet peeve with most consumer products is how difficult they are to clean. Too many nooks, crannies, seams, etc.

I'm planning to buy a Dyson Air Multiplier heater/fan very soon so this comment intrigued me. I'll be sure to go to a store to check them out in advance. I didn't really like the video you linked as I find it to be a bit of a red flag when someone calls something "overpriced", especially when they go on to be very negative about it - it almost feels like jealousy.

Still, I'll look into it before I buy. I don't suppose you know of any other fans/heaters that you would recommend?

I've played with Dyson's Air Multipliers in a department store and they really are that loud when you turn them up to mid-high setting. "Too loud."

I wish I could recommend you a high quality fan, I've looked, and frankly it is pretty slim pickings out there. Currently I have an unbranded Chinese-made one.

I'd kill for an ultra-quiet nighttime one, and pay good $$$ for it too.

Get a ceiling fan, they're usually a lot quieter.

That is because they are much bigger. In general, a larger fan can achieve the same CFM as a smaller fan, but at a lower RPM. Slower spin, quieter operation.

They are bigger, but most people aren't exactly using their ceiling space anyway so that isn't really the downside. The downside is the installation.

A lot of ceiling fans can easily be installed on to an existing light fixture by anyone who knows how to connect a few electrical wires together. I'd say the bigger downside is that it's fixed in one location.

I managed to install mine, and if I can do it anyone can :)

The fact that it's fixed in one location often isn't that much of a problem, given that ceiling lights are traditionally mounted in the center of the room, which is just where you want the fan.

(Traditionally: if you have recessed LED or halogen lighting that would of course be a different matter.)

One warning: if you don't use it all winter, make sure you clean it before you switch it on the first time in spring...

A loud fan doubles as white (?) noise. Helps mask the neighbors, street noise, etc.

You don't have to kill for one. I've had a Lasko tower fan for about three years now. It's almost entirely silent, moves a lot of air, and comes with a remote. I did have to take it apart to regrease the bearings once, but other than that, it's been a great fan. Also comes with a remote.

http://www.amazon.com/s/ref=nb_sb_noss_1?url=search-alias%3D...

Do you have any advice on regreasing the bearings? I've got one of those fans but it's starting to cease up on me.

Yeah, it's a fairly straightforward process. The top bearing isn't actually a bearing at all, but a simple piece of flat steel that basically just holds the top spindle of the blower in place. When you take the fan apart, you'll see what I mean. It's lubricated by some cotton infused with some pretty thin lubricant, and over time, that lubricant/cotton combo loses its lubricity. Mine was starting to make noise, so I took it apart and slathered wheel bearing grease on that contact point, and it's been going for six months now with no problems.

I've found Vornado fans quite powerful and quiet compared to others of the same size.