3 ms·

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.

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).

darkmighty 13y ago
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.
- robomartin 13y ago
  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.
specialist 13y ago
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.
- deleted 13y ago
  [deleted]

darkmighty 13y ago

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.

robomartin 13y ago
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.

specialist 13y ago

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.

deleted 13y ago
[deleted]