Distillation using an air condenser

Quote: Originally posted by Sidmadra

There's this one company that makes a purely glass air condenser that has some really decent reflux power.

Quote: Originally posted by Reboot

Quote: Originally posted by Sidmadra   There's this one company that makes a purely glass air condenser that has some really decent reflux power. Neat! For those on a budget, there's always the classic distillation retort: https://en.wikipedia.org/wiki/Retort You can still buy them on eBay anyway if you're feeling sentimental about the truly old school methods. :-)

Quote: Originally posted by Yttrium2

I'm thinking of yanking apart a nearby fridge to get the copper tube from the ice maker out. Maybe salvage up the polypropylene tubes too The compressor seemed to be more trouble than it was worth last time.

Domestic refrigerators that I have looked at have very small bore tubing,
the condensate would spit out of the tube in bursts and everything start jumping and bumping.
Even with larger diameter tubing you have to ensure that the liquid condensate path is always downhill,
otherwise, drops form into puddles form into traps - and spitting occurs.
I once (Ta c20C) tried a 9mm i.d. 1.5m long glass tube as an air condenser for ethanol heated by a cheap 1500W hotplate;
- 1.5m was not long enough - not all of the vapour was always condensed
- even with a straight, inclined, 9mm bore: 'blobs' of condensate blocked the tube then got spat out.

Just remember, the condenser has to remove the heat of vaporization.
So for me to expect a 1.5m glass tube at below ethanol b.p., in ambient air, to dissipate 100's of Watts was, to say the least - optimistic

I have disposed of refrigerators in the past;
UK/EU regulations are enforced - at least here in West Midlands.
My local council is obliged to collect unwanted refrigerators and freezers FREE OF CHARGE.
Once you break the gas seal you may find it difficult to dispose of.
OTOH
I (my other half) shall soon be disposing of a small fridge and a freezer,
the storage and cooling-power of a used fridge would be great for my chemistry hobby - if I can make some space.

P.S. I now use a calculator for the dissipation of heat by tubes in air.
http://www.paroc.co.uk/tools-and-documents/calculators
and
The intact refrigerator radiator may be useful for re-circulated condenser cooling water, with additional cooling via ice/TEC/refrigeration etc.
or, depending upon production rate, heat of vaporization, condenser efficiency, b.p., ambient temperature...... without additional cooling

[Edited on 21-3-2018 by Sulaiman]

Simple glass tubing works as an air condenser but the cooling power is quite low,
e.g. condensing 100^oC water vapour with 20^oC ambient temperature,
8mm od = 30 W/m, 16mm od = 60 W/m approximately.

So to condense e.g. 100ml water per hour,
2257 (J/g) x 100 (g) /3600 (seconds/hour) = 62.7 W

which would require approx. >2m of 8mm tubing, or >1m of 16mm tubing !

this is why water cooled condensers are so popular
___________________________________________
For high b.p liquids an air condenser is practical,
e.g. b.p. = 320^oC, ambient = 20^oC, diameter = 25mm (one inch)
cooling power is approx. 600 W/m
also
having a 320^oC vapour condensed by 20^oC water would be a 300^oC temperature difference across the glass,
which is a very high thermal gradient that would probably crack the glass.