[mythtv-users] Interesting cooling approach

[Brad Fuller]

On Fri, Feb 29, 2008 at 2:53 PM, Michael T. Dean
<mtdean at thirdcontact.com> wrote:
> On 02/29/2008 05:23 PM, Robin Hill wrote:
>  > On Fri Feb 29, 2008 at 05:00:31PM -0500, Josh White wrote:
>
> >> On Fri, Feb 29, 2008 at 4:43 PM, Larry Sanderson wrote:
>  >>> On Friday 29 February 2008 03:36:41 pm Michael T. Dean wrote:
>  >>>
>  >>>> I--a user who burned out 3 heat pipes on a laptop--will stay away
>  >>>> from /any/ design that uses a heat pipe.  (Especially since my Myth
>  >>>> box is asked to do a /lot/ more work than my laptop ever was.)
>
> >>> Burned out a heat-pipe?  I had no idea that was a common problem.  Did
>  >>> the pipe just burst, or did it spring a leak?  Do you know if this is a
>  >>> problem with a lot of designs?
>  >>>
>  >>> I ask, because a lot of the high-end CPU coolers today employ a
>  >>> heat-pipe design, and I've never heard of one failing.
>  >> What would they leak?  Unless it's liquid cooled, my understanding was that
>  >> a heat pipe was simply a copper pipe, and that heat simply transfered
>  >> through the copper to the heat sink.  Is that assumption wrong?
>  > Yup - see http://en.wikipedia.org/wiki/Heat_pipe - the heat pipe relies
>  > on a fluid changing state between a liquid and a vapour.  The vapour
>  > moves away from the heated end, and the liquid flows back toward it (via
>  > either gravity or capillary action).  The phase changes then take place
>  > at either end, capturing and releasing the heat.
>  >
>  > Oh, and please don't top post.
>
>  Yep.  And given enough heat strain/time, that liquid/vapor will leak.
>  Mother Nature doesn't like it when we humans try to trap her molecules.
>
>  Though, typically, because of the design, a failure of the containment
>  would result in air leaking into the heat pipe (as it's generally
>  pressurized at less than 1 atmosphere) rather than liquid leaking out of
>  the heat pipe.  Then, the liquid would evaporate as it reaches its
>  boiling point at atmospheric pressure.
>
>  Relying on the metal alone to transfer the heat would be far less
>  efficient.  For example, copper (a good conductor of heat) tends to
>  transfer heat at about 1/80 the efficiency of a heat pipe.
>
>  And the fact that I went through three before my laptop was toast (less
>  than 2 years after purchase) indicates it's not just a "tried to use the
>  heat pipe for 15 years" kind of thing (most heat pipes are advertised as
>  having MTTF > 100,000 hours =~ 11.5 years).  It's possible that the heat
>  pipes used on this particular laptop design were faulty, but I wasn't
>  willing to test this theory with my new laptop, so I only use it for
>  web/e-mail/watching video at 480p60 or less/ssh'ing to my "workhorse"
>  systems.  Generally, the laptop CPU remains underclocked to its lowest
>  frequency (half its rated freq).
>
>  Mike

I'm also interested in this problem. What about coolers like Noctua or Scythe?:
http://www.quietpcusa.com/Noctua-NH-U9F-Quiet-CPU-Cooler-with-92mm-Quiet-Fan--P135C41.aspx

http://www.quietpcusa.com/Scythe-Mini-Ninja-Heatpipe-CPU-Cooler-SCMNJ-1000-P304C41.aspx

There seem to be many of these on the market. (I've ordered the
mini-Ninja. I've tried the Zalman fans and they are too noisy)


-- 
Brad Fuller
www.bradfuller.com