[Nottingham] Water cooled CPUs - worthwhile?

Jim Moore jmthelostpacket at googlemail.com
Fri Aug 21 11:32:58 UTC 2009

I don't know why he added the Peltier except possibly to pump heat
directly away from the CPU  and into the block (dry tests looked
pretty good tho), as for the water thing: it's down to the specific
heat capacity of water. At 4.186J/g/K, this is one of, if not the
highest, SHC for any fluid at normal ambient temperature/pressure. To
convert  1Kg of pure water at 373K to 1Kg of steam at 373K requires
2.3MJ (or in real terms, a P4 Cedar Mill processor running at full
load (86W) into a cooling system with no external sink for seven and a
half hours). So for a starting temerature at ambient of 393K, it would
require 2.63MJ to  boil off the entire tank. Given evaporation
effects,  infrared radiation, air convection, and the fact that an
open-tank watercooling system needs topping up every so often (a
technicality most watercooling efficianados solve with a bottle of
distilled cold water near to hand), then the likelihood of a
watercooling system failing  is pretty much lower than a fan spinning
in a single PTFE sleeve bearing at 6000RPM, 24/7/365. We're not going
there with seam leakage.

in one line: you don't need to worry about cooling the water in an
open-tank system, it does it itself.

On 8/20/09, Sergiusz Pawlowicz <sergiusz at pawlowicz.name> wrote:
> On Thu, Aug 20, 2009 at 23:00, Jim Moore<jmthelostpacket at googlemail.com>
> wrote:
>> my brother put together a custom PC  build using convection pumping -
>> no pump or other moving parts,- and his PC ended up totally quiet; the
>> hard drives were attached to heatsinks and then  enclosed in packing
>> foam, he had a custom brass CPU block made with  a built-in Peltier
>> HTU, the whole lot feeding from a 500cc reserve tank. Didn't get any
>> overclocking done, but what he ended up with was enough spare power to
>>  run a few CCT units dotted around the case and a pretty awesome
>> blacklight effect in the  tank itself (and the clear acrylic tubing)
>> by doping the water with Indian ink.and lighting with ultraviolet
>> tubes. The temperature in the reserve tank only ever got around 4C
>> above ambient,  and to my knowledge the kit  still works after nearly
>> five years. I saw it a couple  times, and when I say it was quiet, it
>> didn't even register on my Sennheiser flyspeck tieclip mike and
>> Audacity with the  gain turned full-on.
>> Shop kits usually come with a pump, but if you really find you need
>> one of these, best of fto switch this out for an aquarium pump,
>> they're far quieter.
> afaik peltier must suck as much energy as it drains, so at the end we
> have twice more heat to coo down. i cannot see any reason to use it
> until you want to overclock a cpu.
> i still do not know how to cool down water without a fan.
> s.
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