PABST KG in the Black Forest (Germany) made very quite high efficient
fans, HP used to use these fans for awhile, but the company was sold and
the quite fans disappeared, the new fans from the new owner
http://www.ebmpapst.us/en/ are cheaper but not so quite
73
KJ6UHN
Alex
On 7/15/2016 1:25 PM, Tommy Phone wrote:
Some thirty years ago fans for automotive radiator cooling were designed with 7
unevenly spaced blades to reduce the siren effect yet yield comparable air
flow. Careful layout and blade sweep back along with an annular ring made it
entirely feasible to have a statically and dynamically balanced fan as it came
out of the mold. I always wondered why the folks who make these little fans
can't figure out how to do that. Maybe getting comparable CFM from a much
smaller fan violates some Reynolds number requirement for turbulence control.
From Tom Holmes, N8ZM
On Jul 15, 2016, at 3:52 PM, William H. Fite <[email protected]> wrote:
That is, in fact, precisely how you do it.
On Friday, July 15, 2016, Orin Eman <[email protected]> wrote:
On Fri, Jul 15, 2016 at 10:55 AM, Poul-Henning Kamp <[email protected]
<javascript:;>>
wrote:
--------
In message <
cany2ixq6onvridofgnfkebqjdkntp7t8kue7boupxjwlcux...@mail.gmail.com
<javascript:;>>
, "William H. Fite" writes:
David Kirkby scripsit:
I often here of people replacing fans with quiter ones, but I suspect
that
all they really do is reduce the airflow.
Not necessarily, Dave. The Austrian company, Noctua, for one, makes
extremely quiet fans with excellent airflow.
... at zero pressure differential, which is easy to do (Think: ceiling
fan).
Right.
You have to look at the curves on the data sheet that shows air flow vs.
static pressure (and be careful about the static pressure scale). I found
that a 'quiet' fan would often be flowing one tenth as much air as the
original fan at the static pressure at which the original fan was rated.
In a given instrument, you may get away with the quieter fan, but how would
you tell other than putting a thermometer inside and making a before/after
comparison?
Orin.
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