Heat pipes? - copper - ambient

alvin at Mail.Linux-Consulting.com alvin at Mail.Linux-Consulting.com
Tue Jun 5 00:35:00 EDT 2001


hi ya

> > extruded aluminum is terrible heat conductor but very cheap to make
> > and good enough for slower p3-cpu
> 
> Terrible? 100W/mK - 150W/mK is terrible?

and what would it be if it was NOT extruded ???
( uncut block of aluminum ... than use a very sharp saw to cut your fins
( dont know if laser is good at cutting aluminmum w/o destroy the
( aligned cell structure or whatever its called to allow thermal
( thermal conductivity
  
> > an aluminum block that is cut is "lot better" heat conductor as its
> > molecules are relatively intact ... according to those heatsink
> > manufacturers .. just a few cents more to cut than to extrude ...
> > but when making millions of heatsinks units...guess it adds up...
> > 
> Increasing the surface area of a heatsink or increasing the amount of 
> forced convection across the surface area is how the thermal resistance 
> of a heatsink is reduced.

start with a good thermal conductor... ( in this case copper base )
than worry about resistance .. between the chip and the heatsink
and lots of other variables

> > isnt 68deg still on the high side ??? ....
> 
> The 68 deg C ambient is the air temperature of the environment that the 
> CPU is in. Using a heat sink with a thermal resistance of 0.08 - 0.11 
> degC/W allows us to keep the P4 case temp below the 75 deg C maximum 
> spec. at an ambient air temp of up to 68 deg C. So there is only a 7 deg 
> C rise above ambient.

our ambient was about 25-20 deg c...and the cpu temps was NOT much
higher just a few deg... and 5 or so while running heavy cpu loads

c ya
alvin

> > 
> > some of ofour cpu temp measurements was around 30-35 range...hitting
> > up to  40 or so when runnign heavy loads during the day...
> > 	- the bigger the heatsink got... the hotter the cpu ran too
> > 	cause the itty bitty fans was not good enough ...
> 
> A bigger heatsink doesn't always mean better. Surface area and the the 
> profile is what counts.
> 
> What was your ambient air temp for these mesurements? 20 deg C? -10C? At 
> an average room temp of 20 deg C the CPU case temp would only rise to 27 
> deg C while running at the full 62W max. continuously with the heatsink 
> I mentioned above.
> 


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