RogueRose
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Electric cooling apparatus for fluid circulation
I've come across many experiments where an ice bath is recommended if not required and also have a number of other applications which this would be
very handy.
Basically I'm looking to build something that will chill a solution of some low freezing point liquid (alcohol, anti-freeze, salt solution, etc). I
know a container could be placed in a freezer and then used once cooled but I'm thinking that there may be some other way of doing this such as
placing the cooling coils into an insulated holding vessel of the low FP liquid. A pump could circulate the fluid from the resivoir into the cooling
bath or container or whatever is in need of being chilled.
My question is what can be used as the cooling mechanism as there are a number of appliances that are all basically the same but vary in size and how
long they run (which determines operating temp). I've looked and it seems that fridge/freezers, AC's and even dehumidifiers all use the same
refrigerant in some cases, all use similar compressors. I would think that as long as the plumbing is done correctly (keeping things on the right
level so refrigerant gases flow properly, these appliances could be modified for an application such as this.
On another note, I have seen all 3 of the mentioned appliances ice up when humidity and air flow conditions were not met, so it seems that the temps
are achievable with these.
Has anyone ever used something like this, built one or seen a commercial one in use (how do the commercial ones do it)?
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nlegaux
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I built a chiller/recirculator for all of my condensers using an old dehumidifier. However, I think any equipment with cooling coils could be used as
an alternative (mini fridges, AC units, etc...). This unit will keep tap water at 10*C without any issue. I'm certain it could get much cooler if
antifreeze were added. To make it I added a square bucket to act as a coolant reservoir in which the coils are almost completely submersed. I also
added a fountain pump, a PID (not yet installed in the below photo), and a switch to complete it. In total I spent about $20 building it.
nlegaux
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Photonic
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Similar to nilegaux, I built a refrigerated circulator bath using just a bucket of water, and a compressor out of a mini fridge, and an aquarium pump.
It takes about 2 hours to chill the water down from room temp ~3 gallons, but it will freeze up solid, too, so it gets quite cold.
You can get compressors, and build your own unit and even swap out refrigerants but you'll have to read up on that as each refrigerant has it's own
minimum temperature, and requires varying motor performance to get adequate cooling. E.g. propane may require a more powerful compressor than say
difluoroethane and using it in a compressor not made for it, or something more powerful could burn up the motor for example.
If you want to try to build your own unit look into a book by Bill Whitman, John Tomczyk, Bill Johnson, and Eugene Silberstein "Refrigeration and Air
Conditioning Technology". It should walk you through how the units work, calculation of required BTUs and such application specific formulas.
Don't bother with Peltier coolers as the amount of cooling power is severely limited and they require massive amounts of power to run. I've
experimented with these, and they would be fine if you are cooling say an electronic device like a CCD, but not for cooling any real amount of water
down except in very specialized applications.
You can also pick up some water chillers on ebay for ~$500 or so used but that is probably not what you want to spend either.
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aga
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That is a brilliant idea !
Certainly an idea i can use here ...
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notoxicshit
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That's exactly what I am looking for. Could anyone of the owners of these converted humidifiers describe what is necessary to make it a recirculating
chiller?
Are there tutorials or the like?
There was an awesome thread at www.versuchschemie.de where the admin described converting a mobile air conditioning unit that was already ridiculously powerful, -20°C or more.
The dick put the forum down for whatever reasons and now it's all lost.
I should take a dump at his doorstep because he lives in my city.
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nlegaux
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The exact way you go about modifying an appliance to make it into a chiller depends heavily on exactly how it is made. I would suggest first finding a
piece of chilling equipment (dehumidifier, mini fridge, ac unit, etc...), opening it up, and seeing how it works. If you still can't determine the
best way to convert it after this, I'm sure you can get plenty of help by posting some photos of it here.
nlegaux
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morganbw
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I think you are doing great to think small.
Almost for sure you will need a PID controller or some equivalent to control your cooling/heating media, although on a gentle reaction an on/off
control system can work.
Use your temperature probe (thermocouple or resister type ) to give feedback to the control valve for your cooling/heating media, you will need
something like a 4ma to 20ma transmitter coupled in the control circuit to finish the job. A simple relay circuit can also be used if you do not
require a variable valve system and the reaction is gentle enough.
Heat exchanger can be as simple as a coiled/tubing system immersed into the solution you wish to control the temperature. There is also the option of
a double walled system and if you wish to step outside the amatuar range (plate heat-exchangers are killer for their efficiency.
The cooling and or heating media can be any method of your choice, the control of using it, is key, in many reactions/perhaps most, which require
precision.
I will quit my babbling, I spent nearly twenty years in a career where the reaction temps were very important. Process Control comes into play on many
reactions.
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Photonic
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Quote: Originally posted by notoxicshit  | | That's exactly what I am looking for. Could anyone of the owners of these converted humidifiers describe what is necessary to make it a recirculating
chiller? |
I'm not sure how helpful this is but you rip out the evaporator in a mini fridge being careful not to nick any of the lines or bend them, and then you
put the evaporator in a bucket of water and throw in a aquarium pump.
Here is my setup. It works quite well for my needs.
Here is the evaporator coil. This is the part that gets cold.
This is the one I have for cooling the bucket there I just fill it with water and place it in. You have to be careful to only bend the thing once and
then move the unit as a whole since the lines will break if you stress them too much.
This is the unit in the bath with the aquarium pump at the bottom. It would be filled with water when in use.
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