On Monday 11 November 2002 22:28, Gareth Randall <[EMAIL PROTECTED]> wrote: > > The front air intake vents on almost every PC case I have ever seen have > been virtually *useless*. For some reason manufacturers continue to drill a > few pathetically small holes in the steel sheet and call that an air duct. > People then put case fans against these and try to suck against what is 90% > metal sheet and wonder why not much happens.
Hmm. I know exactly what you mean, but they're not _all_ like that. Look at e.g. the Coolermaster range. > > What you should do is to take a saw or a drill and cut the whole circular > section out! You may end up with sharp edges, and you need to take > precautions against metal shavings. You may also need to drill some neat > holes (e.g. 10mm diameter) in the plastic front bezel in order to provide > an unimpeded air path. Do the job _before_ you install components (or remove everything before commencing surgery). File down the inevitable sharp edges, finishing with fine emery cloth, or wet-and-dry paper. Thoroughly remove swarf right down to metal powder - personally I think it's best to wash out with a high-pressure hose, then allow to dry. At least think about installing a grille to protect fingers & the inevitable stray bits of cable from rotating fan blades. It also helps - long term - to place a piece of open-cell foam, or a layer of filter material intended for use in a vacuum cleaner, in the inlet(s). The idea is that much of the dust drawn in will stick in this - where it can be got at easily - rather than end up getting stuck in heat sink fins etc. where it will have a serious effect. Suitable material can be cut with scissors & held in place by a grille. > > Nevertheless, when the procedure is done you should be able to hold a match > in front of a machine with nothing other than the PSU fan and see the flame > visibly sucked into the case. > > If your airflow can't do that, then any internal fans you deploy are going > to be pulling on a vacuum (or rather, reduced pressure). If it can do that, > then you are in a *much* better position to keep your number cruncher cool > and reliable! Some other points here: (1) fans working in a badly restricted air flow are probably going to be noisier than they should be, as they will be running with stalled airflow over the blades, causing excessive turbulence. When the airflow is reasonably free, the air flow over the blades will be much less turbulent. (2) It seems to make sense that the fans in the case (including those in the PSU) should be arranged so that roughly equal volumes are blown in and sucked out. Otherwise one or other of the fans will very likely be running with stalled fan blades. Also, obviously, it helps if the path between inlet and outlet passes things you want to cool down - there's not much point in having inlet air blown straight back out before it has a chance to warm up. (3) Other things being equal, large fans are quieter than small ones with the same air flow, since the rotation speed is lower and there tends to be less turbulence. Two low-output fans are preferable to one high-output fan for the same reason. Regards Brian Beesley _________________________________________________________________________ Unsubscribe & list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
