[time-nuts] Thunderbolt stability and ambient temperature
namichie at gmail.com
Sat Jun 13 18:02:35 EDT 2009
Water must have a fairly high figure of merit for thermal buffering.
Unfortunately the lists of material properties are inaccurate, have
and are inevitably listed in units such as tons per Degree F per inch
per square foot.
The tons refer to tons of ice per 24 hours, a good old reliable air
The relevant measures are thermal conductivity, thermal heat
and thermal diffusivity.
Now there is an interesting comparison between copper and aluminium.
Copper has a specific heat of 0.09 and aluminium 0.2. (cal/gm C )
Copper has a relative thermal conductivity of 0.918 and aluminium 0.48
Copper has a density of 8.9 and Al 2.7
So the heat capacity of copper is 0.8 and Al 0.54 cal/C/cc when
calculated on a volume basis.
So water at 1cal/C/cc is better than copper, and twice as good as
Where water really wins is on price, and being a liquid it will heat
with convective circulation
and so be much faster than the solids to reach equilibrium.
cheers, Neville Michie
On 14/06/2009, at 4:14 AM, Chuck Harris wrote:
> Yes, but if it takes 20 years for 1 tsp of water to be lost, I just
> don't see how that rules out the use of water as a thermal ballast.
> Water's cheapness and availability in bulk makes it quite attractive
> for this purpose.
> If you don't trust plastic, use copper, or stainless steel, or...
> If man can keep a vacuum in a vacuum tube for 100 years, surely
> keeping a little water in a bottle or can isn't that hard?
> Besides, I don't think we were talking about putting the water inside
> of a crystal oven. We were talking about using water as a thermal
> ballast to keep the closet/box your standard occupied at a more stable
> -Chuck Harris
> J. Forster wrote:
>> Chuck, I don't dispute that you can contain water in plastic a
>> long time,
>> but, if some does escape it may not matter to the bottle contents,
>> but it
>> could well raise the humidity of the surround w/in a tightly sealed
>> oven/box/enclosure. Electronics does not much like high humidity.
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