Date: Tue, 08 Jun 2004 13:45:35 -0700 From: Jason Taylor <jason@infinitebubble.com> To: Bill Moran <wmoran@potentialtech.com> Cc: freebsd-questions@freebsd.org Subject: Re: [Going further OT] Re: Leaving a server on all day Message-ID: <40C6256F.5040800@infinitebubble.com> In-Reply-To: <20040608161145.0a4b2525.wmoran@potentialtech.com> References: <20040608122101.GA68204@dogma.freebsd-uk.eu.org> <20040608184216.GA4231@panix.com> <20040608185151.GD70798@dogma.freebsd-uk.eu.org> <20040608190514.GA6271@panix.com> <20040608191506.GE70798@dogma.freebsd-uk.eu.org> <40C61BB7.50805@zonnet.nl> <20040608161145.0a4b2525.wmoran@potentialtech.com>
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Bill Moran wrote:
> Nico Meijer <nico.meijer@zonnet.nl> wrote:
>
>>Hi,
>>
>>
>>>What is so bad with the floor?
>>
>>Ever move into a beautiful house only to find the floor *flooded* at the
>>first serious cloud break? ;-)
>>
>>BTW - I'd make sure I'd get/have a decent computer case with a decent
>>PSU with enough room for some decent 80mm or larger low noise fans
>>rather than opening up the side panel. Perhaps an aluminum (Chieftec
>>Dragon, anyone?) case with some Enermax and Zalman coolers and PSU might
>>do the trick. I've {b,s}een told a good airflow (front to back) is king.
>
>
> I saw an article recently by a guy who had a degree in thermal dynamics or
> something that was dispelling the common myths about PC cooling.
>
> His conclusion was basically that airflow is king. You need to move air across
> the heat sinks that is cooler than the heat sinks are. Sounds simple, but the
> overall conclusion was that you could improve cooling without increasing noise
> by ensuring that air from _outside_ the case was flowing directly over the
> processor heatsink. Reason this works well is becuase the air inside the case
> is usually considerably warmer than the air outside the case, and moving warm
> air across the heat sink doesn't accomplish much. By drawing cool air in from
> outside the case, things stay cooler.
>
> Anyway, his suggestion was that the best thing you could do for your cooling
> rig was to purchase/fab one of those little duct kits that allows the cpu fan
> to pull air from outside the case. Some cases even have the duct built in (my
> brother's computer does).
>
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. Of course, the fluid has to be
cooler than whatever is being cooled. A fan rotating at certain speed
is going to push a given volume of air in a given amount of time. By
leaving the case covers on and providing only a few small "holes" for
the air to travel through, you're going to force the air coming through
those holes to travel through the case faster.
That being said, if the case design, component placement, etc. is such
that leaving the the cover off actually allows a significantly greater
volume of air to get to the heatsink(s) in a given amount of time, then
leaving the cover off is a good thing.
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