[Greenbuilding] Speed of ceiling fan
RT
Archilogic at yahoo.ca
Wed Aug 31 15:17:00 CDT 2011
On Wed, 31 Aug 2011 09:55:00 -0400, Sacie Lambertson
<sacie.lambertson at gmail.com> wrote:
> John, honing in on that last bit regarding the fan moving at 200 mph
> over a body, what is the speed of a ceiling fan--at the low, middle and
> high
> speed?
Assuming that the question actually is:
"What air velocity does a ceiling fan yield at the LOW, MEDIUM and HIGH
speed settings ?"
Obviously the air velocity (and hence the cooling effect one feels) would
vary with fan blade size, fan motor size, ceiling height, downrod length,
distance of the person away from the face of the fan etc.
ie A person standing 8 inches away from the fan blades of an 8 ft diameter
fan driven by a 1/2 HP direct drive motor with the fan speed set on HIGH
may very well feel like the fan is moving air past her face at 200 mph(!).
However, a person standing 12 feet down and 20 feet away from the face of
a 42 inch Home Despot ceiling fan or even 2 feet away from a little
computer fan might feel negligible air movement and negligible cooling
effect.
To determine air velocity one typically uses an anemometer (various types
exist), and typically, it's an item that most people don't have hanging
around in their "miscellaneous tools" drawer.
For Sacie's purposes, I suspect that a rudimentary anemometer could
probably be rigged up using a bicycle with a front wheel (preferably
reasonably well trued) whose bearings have been well greased (so that it
spins with a minimum of friction) and which has a bicycle computer
attached. The latter are available for less than $10, delivered to your
mailbox and are capable of a $#!+-load of functions (ie odometer, trip
odometer, maximum speed,average speed, elapsed time, time of day clock,
temperature ... and instantaneous speed, usually in your choice of miles
per hour or kilometres per hour.
200 ft per minute = ~ 3.7 kph
For the arithmetically-challenged:
(kilometres per hour) x ((1000 x 3.281) / 60) = feet per minute
So it would be a matter of laying the bike on its side so that the front
wheel (with the speed sensor) spins freely and then maybe you tape some
paper cups or some old DD bra cups or such-like at say, a minimum of 8
spots around the edge of the wheel to "catch" the wind. Turn on the fan
and hopefully the bike wheel starts spinning and VOILA! The LED display of
the bike computer should eventually tell you the air velocity once the
wheel gets up to a constant speed. (Note: I've *not* tried this at home. I
am a professional.)
--
=== * ===
Rob Tom
Kanata, Ontario, Canada
< A r c h i L o g i c at Y a h o o dot C A >
(manually winnow the chaff from my edress if you hit REPLY)
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