Vario flask insulation

Bill,

Use a vacuum flask and put 2 or 3 copper pot scrubbers (chore girl
brand works OK) in the bottle, then cap the bottle and make sure you
test for leaks. Leaks on the bottle side of a vario make for huge
errors.

Jim

Bill Daniels wrote:
snip
Clearly, as every instrumentation book says, the flask has to be
insulated. The purpose of the above narrative is leading up to the
question about the best material to insulate the flask. I want to mount
the flask behind the instrument panel to keep the tubing runs as short as
possible.

What's the best insulation material?

Bill Daniels

A vacuum

Michael McNulty wrote in message news:DCLMb.408$
A vacuum

Awwww. you cheated, that's not a 'material'....isn't a vacuum a lack
of material?? ;-)

At 14:00 13 January 2004, Andy Durbin wrote:

I thought the pot scrubbers were used to reduce the
flask capacity to
compensate for the capacity added by a long tubing
run.

Andy

Andy,

You can fill a pint beer glass with water to the brim
and then slowly introduce a fine pot scrubber wihout
spilling a drop if you are careful. I can't remember
where I first heard that but I didn't believe it until
I tried it.

John Galloway

You can fill a pint beer glass with water to the brim
and then slowly introduce a fine pot scrubber wihout
spilling a drop if you are careful. I can't remember
where I first heard that but I didn't believe it until
I tried it.

John Galloway

What a waste of beer! Hopefully the scrubber didn't have any soap or
detergent? 8-)

Keith

John Galloway wrote in message ...
At 14:00 13 January 2004, Andy Durbin wrote:

I thought the pot scrubbers were used to reduce the
flask capacity to
compensate for the capacity added by a long tubing
run.

Andy

Andy,

You can fill a pint beer glass with water to the brim
and then slowly introduce a fine pot scrubber wihout
spilling a drop if you are careful. I can't remember
where I first heard that but I didn't believe it until
I tried it.

John Galloway

That seems to say that the volume of copper is *very* small so its
mass would be too. Is there any useful heat exchange between a
negligible mass of copper and .45 litres of air?

I'll add the knowledge to my useful pub tricks list though.

Andy

On Tue, 13 Jan 2004 20:47:07 UTC, (Andy Durbin)
wrote:

: That seems to say that the volume of copper is *very* small so its
: mass would be too. Is there any useful heat exchange between a
: negligible mass of copper and .45 litres of air?

I bet the trick wouldn't work if the glass was really, really full.
You can pile a lot of water up in a meniscus.

That said, the specific heat capacities for copper and air are 380 and
1004 J/kgK, but since the densities are 896 and 1.225 kg/m^3, the
volumetric heat capacities are 340 and 1.23 kJ/Km^3, a ratio of 276:1.
In other words, filling 1% of the capacity with copper will nearly
treble the heat capacity of the, um, capacity.

Ian
--

"Ian Johnston" wrote in message
news:cCUlhtvFIYkV-pn2-slrYLOWSYEIp@localhost...
On Tue, 13 Jan 2004 20:47:07 UTC, (Andy Durbin)
wrote:

: That seems to say that the volume of copper is *very* small so its
: mass would be too. Is there any useful heat exchange between a
: negligible mass of copper and .45 litres of air?

I bet the trick wouldn't work if the glass was really, really full.
You can pile a lot of water up in a meniscus.

That said, the specific heat capacities for copper and air are 380 and
1004 J/kgK, but since the densities are 896 and 1.225 kg/m^3, the
volumetric heat capacities are 340 and 1.23 kJ/Km^3, a ratio of 276:1.
In other words, filling 1% of the capacity with copper will nearly
treble the heat capacity of the, um, capacity.

Ian
--

I've been doing some searching for a 0.45L vacuum flask - no luck. All
consumer thermos bottles these days are heavy, bulky, not very insulating
stainless steel. Laboratory glassware suppliers do sell 500ml glass dewars.
The ones that I could find however, are short, wide mouth containers which,
with the large rubber stopper required, wouldn't be very good either.

Anybody got a lead on a narrow-mouth, half liter glass dewar?

The other approach is to use the tan plastic 0.45 liter capacity flask that
comes with varios these days like the one that failed the test for thermal
effects. Insulating one of these might be acceptable but there is no way to
insert a copper scrub pad.

Bill Daniels

Earlier, "Ian Johnston" wrote:

...You can pile a lot of water up in a meniscus.

I think you just named Pez's next sailplane!

"Andy Durbin" wrote in message
om...
snip
That seems to say that the volume of copper is *very* small so its
mass would be too. Is there any useful heat exchange between a
negligible mass of copper and .45 litres of air?

I'll add the knowledge to my useful pub tricks list though.

Andy

Rather than squeeze this out a piece at a time, take a look at:
http://www.betsybyars.com/guy/soarin.../69-vario.html

and get a perhaps-useful overview.

Tim Ward