Swamp coolers do work. However, a little jotted-down math shows that the strips on fans are simply too small to make any difference from evaporative cooling. In any case, whenever I’ve seen them, the strips have been plastic. They’re just for show.
In a lab, we use them as “telltales” on ventilation just to let us know if a fume hood is working (at all–we call in the pros to measure fps air flow).
We have a ribbon on our fan to keep the cat entertained. Works really well, he will play with it for hours!
In a store the visual queue is used to draw the shopper’s attention to the fan. It is a way for the store to have the fan say, “Buy me!” The eye is attracted to movement, and spinning blades are often “invisible”. (That’s why propeller and rotor tips on aircraft are painted a bright colour, and helicopters have a big arrow that says “DANGER” pointing at the tail rotor – to warn people not to walk there.) Also, many fans’ blades are hidden behind grillework and can’t be seen at all.
In a television commercial the spinning blades are harder to see than IRL. Also, television is a medium that favours movement. The ribbons show the movement better than just having the fan sit there. This is one reason why most car commercials show the car on the road. While we can intellectually see (usually) that a fan is running, adding the ribbons hits us in our subconscious which is often more effective in advertising than an intellectual appeal.
When I was a kid stores would have a cannister vacuum cleaner on display. The exhaust port would be pointed up (either by design or by using one of the accessory hoses) and a beach ball would be balanced on the stream of air. It would spin and bob and generally call attention to itself, while the aerodynamics kept it from falling away. It always caught my eye, and I presume it would be just as effective with the money-bearing adults.
i have seen some office’s ‘aircon outlets in the ceiling’ thingys with the strips too, presumably to show that it’s working at a glance…
I’d say at least 80% of the floor models I’ve ever seen in stores have employed this effect. It’s more common to use strips of plastic(oddly, they’re almost always blue, silver and white), not ribbon or cloth, though. I think I’d be suprised to see a fan in a store without the foolish pieces of plastic flapping so you see how “powerful” the fan is, to tell the truth. So, at least in this area, it’s done in real life.