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Author: Subject: Water cooling for reflux condenser for 24 hours? Ice melts quickly, other set and forget options?
beerwiz
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[*] posted on 26-11-2018 at 00:49
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]
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froot
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[*] posted on 26-11-2018 at 01:27


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]




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Sulaiman
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[*] posted on 26-11-2018 at 02:54


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 :P
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]




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CouchHatter
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[*] posted on 26-11-2018 at 07:56


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.
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Loptr
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[*] posted on 26-11-2018 at 08:06


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. :cool:




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Herr Haber
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[*] posted on 27-11-2018 at 04:30


+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.
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AvBaeyer
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[*] posted on 28-11-2018 at 19:47


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
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Ubya
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[*] posted on 29-11-2018 at 01:47


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




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Tsjerk
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[*] posted on 29-11-2018 at 08:02


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.
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kulep
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[*] posted on 29-11-2018 at 08:46


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 )

62e67449_WP_20140729_001.jpeg - 450kB

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]
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Tsjerk
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[*] posted on 29-11-2018 at 09:35


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.
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Ubya
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[*] posted on 29-11-2018 at 14:53


this is a cool idea, i thought about it but just as theory, never planned on building such a device, anyway COOL




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Safety_Lucas
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[*] posted on 8-12-2018 at 20:30


Get a PC radiator from eBay and attach a PC fan to it. I've been using this method for years with great success.
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kulep
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[*] posted on 9-12-2018 at 08:03


Quote: Originally posted by Safety_Lucas  
Get a PC radiator from eBay and attach a PC fan to it. I've been using this method for years with great success.


Yes but with many solvents you can't use 50c water
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[*] posted on 9-12-2018 at 08:29


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...



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Safety_Lucas
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[*] posted on 9-12-2018 at 11:22


Quote: Originally posted by kulep  

Yes but with many solvents you can't use 50c water


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]
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