hi,
the main point of the water approach was the high performance of
water as a heat storage medium.
Quartz, if one can assume that is what pebbles are made of, has a
density of 2.7 g/cc but a specific
heat of only 0.2 cal/gm C.
That is only 0.54 cal/cc C compared to water with a figure of 1.0.
So water still has greater merit as a thermal buffer.
Cheers, Neville Michie
On 16/06/2009, at 2:30 AM, Joseph M Gwinn wrote:
[email protected] wrote on 06/15/2009 06:57:13 AM:
They suggest you add a small amount of chlorine bleach to water
containers you store for natural disaster emergencies. You also need
to replace the water on a regular basis even with the bleach in it.
Here in Christchurch, New Zealand, they don't even chlorinate the
water we drink, it comes straight out of a natural aquifer underneath
us. As for the long term effects of bleach on plastic bottles, one
would imagine that it would accelerate the breakdown of the plastic.
Interestingly, someone in the know, talking about land-fill sites,
suggested that there is essentially no breakdown of these items when
they are fully embeded in the fill. Luckily we recycle almost
everything here but it would make interesting finds for future
archaeologists.
A glass vessel with a stabilised rubber stopper or lapped glass
stopper and wax sealed would seemingly be better for long term use
and
the glass should conduct the heat better than plastic for our xtal
oven ballast. But glass is not a solid, it's a liquid after all and
would eventually find the lowest point with time. Mind you, that is a
very long time. The other thing that comes to mind is that
state-change salt type of liquid that absorbs energy well. Of course,
you could use an eskey if it was not holding the beer and may be a
less smelly alternative than a used fridge at room temp.
I was the one who originally rained on the use-water-in-a-bottle
approach.
The response was that even a child could store water. Well, that
is not
the common experience with water-cooled equipment, which always
manages to
require continual maintenance attention, so I went quiet, and
listened as
the subject was explored.
It has become apparent from the issues and increasingly complex
schemes to
solving tose issues that keeping water in its place is not exactly
child's
play, and it seems to me that water is far more trouble and even
expense
than simply getting a big hunk of scrap metal, unless one needs
tons of
thermal mass. If one needs fast thermal exchange with the air,
drill some
holes or use a set of thick plates with spacers, so the distance
from air
to the most remote part of the mass is no more than an inch or so.
Or,
use a big hunk of copper or aluminum. Or both.
If one needs tons of thermal mass plus rapid exchange with the air,
use
brick checkerwork or a pebble bed, a standard industrial approach: <
http://en.wikipedia.org/wiki/Regenerator>. For thermal
stabilization of
timekeeping equipment, a pebble bed and a circulating fan is cheap and
easy.
Joe Gwinn
73,
Steve
2009/6/15 Didier Juges <[email protected]>:
Here in Florida, we routinely store water in prevision of the
next big one.
Plastic water bottles (any brand) start looking funny
(shrunk) after a few
months, and downright scary (as in: you don't want to drink
from THAT) after
a year or so.
It seems the gallon jugs do somewhat better than the smaller
bottles. I had
jugs that still looked OK after a year, but not good after
two. The pastic
seems much thicker, and maybe it slows down the process?
It's been like that for as long as I have lived here, i.e.
since 1985. I do
not know if it is related to the climate. It makes no
appreciable difference
if the water is stored in the garage (no A/C) or in the house.
Didier KO4BB
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Thomas A. Frank
Sent: Saturday, June 13, 2009 12:16 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Thunderbolt stability and ambient
temperature
More to the point, you will be disappointed to find the bottles
will
NOT last that long.
Cleaning out the cupboard recently, I can across some bottled water
that had 1998 date codes. Several had leaked, but one was still
intact enough to show the likely problem. It would appear that
over
the past 10 years, the gases dissolved in the water migrated
through
the plastic (or the cap seal), resulting in a vacuum forming in the
bottle. This distended the bottles and caused structural failure.
Either that, or the water caused the plastic to shrink.
Glass would probably fair better.
Tom Frank, KA2CDK
_______________________________________________
time-nuts mailing list -- [email protected]
To unsubscribe, go to https://www.febo.com/cgi-
bin/mailman/listinfo/time-nuts
and follow the instructions there.
--
Steve Rooke - ZL3TUV & G8KVD & JAKDTTNW
A man with one clock knows what time it is;
A man with two clocks is never quite sure.
_______________________________________________
time-nuts mailing list -- [email protected]
To unsubscribe, go to https://www.febo.com/cgi-
bin/mailman/listinfo/time-nuts
and follow the instructions there.
The following line is added for your protection and will be
used for analysis if this message is reported as spam:
(Raytheon Analysis: IP=64.34.164.147; e-from=time-nuts-
[email protected]; [email protected];
date=Jun 15, 2009 10:59:08 AM; subject=Re: [time-nuts]
Thunderbolt stability and ambient temperature)
_______________________________________________
time-nuts mailing list -- [email protected]
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/
time-nuts
and follow the instructions there.
_______________________________________________
time-nuts mailing list -- [email protected]
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
