Date: Tue, 8 Jun 2004 18:17:34 -0400 From: Bill Moran <wmoran@potentialtech.com> To: freebsd@pursued-with.net Cc: freebsd-questions@freebsd.org Subject: Re: [still going ... OT] Re: Leaving a server on all day Message-ID: <20040608181734.016cd13b.wmoran@potentialtech.com> In-Reply-To: <Pine.OSX.4.58.0406081450470.569@onorysvfu.chefhrq-jvgu.arg> References: <20040608122101.GA68204@dogma.freebsd-uk.eu.org> <20040608185151.GD70798@dogma.freebsd-uk.eu.org> <20040608191506.GE70798@dogma.freebsd-uk.eu.org> <20040608161145.0a4b2525.wmoran@potentialtech.com> <40C6256F.5040800@infinitebubble.com> <Pine.OSX.4.58.0406081450470.569@onorysvfu.chefhrq-jvgu.arg>
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Kevin Stevens <freebsd@pursued-with.net> wrote: > > On Tue, 8 Jun 2004, Jason Taylor wrote: > > > Ok, I'll chime in here. Here's what everything I ever learned about > > heat transfer and fluid flow tells me: > > > > Everything Bill is saying is correct. The best way to cool is to move > > as much fluid (air is a fluid for the purpose of this discussion) as > > fast as possible across whatever is hot. > > As a point of interest, "as fast as possible" isn't always correct, though > it may be WRT practical case-cooling considerations. One consideration in > designing race cars, especially those using stock engines, is to not > overdrive the water pump at high rpms. Not because of cavitation, because > you can flow water through the engine faster than is optimal for heat > dissipation. Non intuitive, but true - has to do with the heat transfer > across the water/metal surfaces and is otherwise over my head. ;) I think the original point of my post was lost. Looking back, I don't think I explained it well. The author's point (damn ... wish I had saved a link to that URL) is that temp differential is more important than air volume. The upshot being that by bringing air in from the outside of the case (which is cooler) you can run slower fans (thus have a quieter system) and have the same quality of cooling. The flip side is that if you need _more_ cooling, you can keep the same speed fans, and by using cooler air you end up with better cooling overall. -- Bill Moran Potential Technologies http://www.potentialtech.com
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