beerwiz
Hazard to Others
Posts: 130
Registered: 6-2-2014
Member Is Offline
Mood: No Mood
|
|
Water cooling for reflux condenser for 24 hours? Ice melts quickly, other set and forget options?
Refluxing ethanol for 24 hours. Using some ice in a container with a recirculating pump but the ice melts within the hour and I'm not able to replace
it constantly. I'd prefer a set and forget method.
How would you keep supplying cool water for the reflux condenser for 24 hours?
I would use the cold water from the faucet as a last resort. Any other options?
[Edited on 26-11-2018 by beerwiz]
|
|
|
froot
Hazard to Others
Posts: 347
Registered: 23-10-2003
Location: South Africa
Member Is Offline
Mood: refluxed
|
|
Not sure what scale you're working at and what your max temp needs to be but what about Peltier CPU coolers?
If you need to be near 0 degC then compressor driven refrigeration would be the way to go.
Or... Increase the volume of your ice by filling a cooler box or 5 and circulating your cooling water through that.
[Edited on 26-11-2018 by froot]
We salute the improvement of the human genome by honoring those who remove themselves from it.
Of necessity, this honor is generally bestowed posthumously. - www.darwinawards.com |
|
|
Sulaiman
International Hazard
Posts: 3698
Registered: 8-2-2015
Location: 3rd rock from the sun
Member Is Offline
|
|
As the b.p. of ethanol is well above ambient temperature you can use passive cooling / an air-cooled condenser.
Something with a lot of surface area will be required.
A short length of copper pipe will be inadequate, glass even worse.
(please check but, for 15mm copper pipe use at least one inch per Watt)
Whatever passive cooling is used,
you can add a small water-cooled condenser at the top just to be sure,
it should not be needed therefore should not consume much ice - if insulated.
Alternatively the condenser can be water cooled,
with the water itself being cooled by circulation through a radiator / heat exchanger.
A small water pump provides the water circulation.
I tried using temperature/density gradients to passively pump water around the condenser and radiator,
it worked but not to my sattisfaction.
I hope to re-visit this someday.
As winter is comming to the Northern hemisphere passive cooling becomes very simple,
(unless you are not in the Northern hemisphere 
when ambient air temperatures are higher the performance will be much poorer.
Afterthought: UNTRIED
You could probably use a large conventional reflux condenser using pumped ambient air instead of water.
i.e. an air pump instead of a water pump.
[Edited on 26-11-2018 by Sulaiman]
CAUTION : Hobby Chemist, not Professional or even Amateur
|
|
|
CouchHatter
Hazard to Others
Posts: 152
Registered: 28-10-2017
Location: Oklahoma
Member Is Offline
Mood: 76 elements taken!
|
|
I've got insulated 1/2" lines running from a pump inside a jug of slush in my freezer. Looks bad though, and my homemade foam freezer seal is less
than perfect. Still, i never need to buy ice. Not sure if I'm saving money in the end but it's definitely set-and-forget.
|
|
|
Loptr
International Hazard
Posts: 1348
Registered: 20-5-2014
Location: USA
Member Is Offline
Mood: Grateful
|
|
I have a mini chiller that I got off eBay.
https://www.amazon.com/Huber-Minichiller-Water-cooled-Chille...
I didn't pay anywhere near what its listed for on Amazon. 
"Question everything generally thought to be obvious." - Dieter Rams
|
|
|
Herr Haber
International Hazard
Posts: 1236
Registered: 29-1-2016
Member Is Offline
Mood: No Mood
|
|
+1 for the mini chiller
+1 for the faucet during winter
Animal stores. Specially the ones selling fish have water heaters, water coolers and tubing for far less than chemistry suppliers.
Those same coolers are also used in hydropony.
Or for cooling beer while it is being served.
|
|
|
AvBaeyer
National Hazard
Posts: 651
Registered: 25-2-2014
Location: CA
Member Is Offline
Mood: No Mood
|
|
Beerwiz raises a a particularly perplexing problem for the home lab. I have faced the same problem a number of times. Without investing in expensive
recirculating coolers or running water all night the solution is not immediately obvious. However, when I was working at the bench in my younger years
we were advised/told not to run condenser water all night as fluctuations in water pressure sometimes led to popped hoses and floods into the biology
labs below or reactions boiling away because water flow stopped. We solved the problem in the following way. We realized that the purpose of refluxing
solvent was to maintain a constant reaction temperature. So the reaction to be run was immersed in a constant temperature bath just below the boiling
point of the reaction solvent. The reaction vessel was fitted with a condenser without water. When the temperature of the reaction mixture had reached
the bath temperature a stopper was fitted to the top of the condenser. Both the stopper and the condenser were held fast with rubber bands (we did not
have Keck clips). The rubber bands also provided some means of pressure release. This method was used routinely without incident. However, success
requires a reliable way to ensure a constant bath temperature. I still use this method routinely in my home lab. I just finished running a reaction in
acetone at 55C for 24 hours which normally is run under reflux and it worked just fine. I use a ChemGlass stirrer-hotplate with a programmable
temperature probe and an oil bath. Granted, this is not a cheap piece of equipment, but it solves the problem. There may be other workarounds to
achieve reliable constant temperature control, but the method works fine.
AvB
|
|
|
Ubya
International Hazard
Posts: 1247
Registered: 23-11-2017
Location: Rome-Italy
Member Is Offline
Mood: I'm a maddo scientisto!!!
|
|
but reflux is also used because most of the time the solvent evaporates easily, if you need to reflux at the boiling point of the solvent you really
need active cooling of the column
---------------------------------------------------------------------
feel free to correct my grammar, or any mistakes i make
---------------------------------------------------------------------
|
|
|
Tsjerk
International Hazard
Posts: 3032
Registered: 20-4-2005
Location: Netherlands
Member Is Offline
Mood: Mood
|
|
If you use a water pump in a big bucket of water and reflux at a low rate you don't need cooling for ethanol, the water in the bucket will lose heat
fast enough. Ethanol isn't that hard to condense.
|
|
|
kulep
Harmless
Posts: 46
Registered: 19-5-2018
Location: Somewhere below the tropic of Capricorn
Member Is Offline
Mood: Spicy
|
|
What about a "bong" evaporative cooling tower?
https://www.overclock.net/forum/134-cooling-experiments/1503...
I think this would be the best cheap option for the amateur. Before someone says 'but I live in the middle of the swamp that won't work here' just
think that if the water gets just a bit above ambient temp the evaporation rate would increase quite a lot, we don't necessarily need temps below
ambient, we need them to be not so high above ambient.
Of course if you live in a very dry area you could achieve pretty low temps.
In the forum post I linked above they used a showerhead or something like that, I think an atomizer like the ones weed sprayers have might be better.
Also some kind of cloth could be used inside for more air turbulence and surface area.
One thing to keep in mind is that it can become a biological weapon ( https://en.wikipedia.org/wiki/Legionnaires'_disease )
There's an atomizer in the top of each column, the fans are blowing air through the falling water droplets, very humid air exits the top.
[Edited on 29-11-2018 by kulep]
|
|
|
Tsjerk
International Hazard
Posts: 3032
Registered: 20-4-2005
Location: Netherlands
Member Is Offline
Mood: Mood
|
|
As far as I see quickly a couple of drops of bleach wouldn't hurt the installation, which would do wonders for avoiding it becoming a biological mess.
|
|
|
Ubya
International Hazard
Posts: 1247
Registered: 23-11-2017
Location: Rome-Italy
Member Is Offline
Mood: I'm a maddo scientisto!!!
|
|
this is a cool idea, i thought about it but just as theory, never planned on building such a device, anyway COOL
---------------------------------------------------------------------
feel free to correct my grammar, or any mistakes i make
---------------------------------------------------------------------
|
|
|
Safety_Lucas
Harmless
Posts: 6
Registered: 28-9-2017
Member Is Offline
Mood: Radical
|
|
Get a PC radiator from eBay and attach a PC fan to it. I've been using this method for years with great success.
|
|
|
kulep
Harmless
Posts: 46
Registered: 19-5-2018
Location: Somewhere below the tropic of Capricorn
Member Is Offline
Mood: Spicy
|
|
Yes but with many solvents you can't use 50c water
|
|
|
WGTR
National Hazard
Posts: 971
Registered: 29-9-2013
Location: Online
Member Is Offline
Mood: Outline
|
|
If you want to splurge, a Bernard 3500SS is awesome. There's a powerful motor-driven water pump and fan, a water tank, and a radiator for cooling. I
used to have one of these for TIG welding. Lots of stainless steel on these. Discontinued now, but there are used ones here and there.
https://www.ebay.com/p/Bernard-3500SS-Water-Cooler-MIG-TIG-W...
|
|
|
Safety_Lucas
Harmless
Posts: 6
Registered: 28-9-2017
Member Is Offline
Mood: Radical
|
|
50C? The radiator keeps the water inside of it very close to room temperature. Hopefully you aren't trying distillation in the desert! As you alluded
to though, you can get down to the wet bulb temperature just by evaporating water. Maybe what you could do is use a PC radiator with a fan and have a
separate supply of water that is atomized or wicked over the radiator to give lower temps. That would also keep the biologicals outside of your
cooling water.
[Edited on 12-9-2018 by Safety_Lucas]
[Edited on 12-9-2018 by Safety_Lucas]
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
