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. >> _______________________________________________ >> time-nuts mailing list -- [email protected] <javascript:;> >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > > > -- > Yes, Black lives do matter. > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
