Currently building a setup which will have 2x 3-phase chillers and 2x 240v heating circulators. The plan is to use one chiller on the drop coil in the solvent tank and set around -60c. The other chiller will be connected to a heat exchanger and the material column and run at about -40c. One heater will connect to the collection vessel while the other will will also be connected to the material column.
My question is about which fluids to use. It seems like most around here are using alcohol for the ultra low temp side, so 200 etoh? Or diluted? Isopropyl? The heptane-spiked crap?
For the chiller and heater that will be sharing fluids via the material column jacket, can I just use a 50:50 ratio of ethylene glycol and water or will that get slushy at -40?
Any help would be greatly appreciated.
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The glycol water mix will probably slush up at -40
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whatever you use you will need to keep it dry, some chillers use dry n2 gas in the head space of the chiller resivour to displace any moisture ridden air from the atmosphere. Iso, acetone, or a heat transfer fluid like syltherm xlt. Make sure whatever you use is compatible with the chiller.Ice is a chiller killer!
For the hot side concentration check this out
Glycol Calculator - VAPCO Company - Innovating HVACR
you may want to use corrosion inhibitors as well, glycol is kinda corrosive.
Also you may need to routinely check the concentration of the solution, use a brix hydrometer like this. https://www.coleparmer.com/i/cole-parmer-rsa-br32t-refractometer-w-atc-0-32-brix/8115036?PubID=UX&persist=true&ip=no&gclid=Cj0KCQjw-af6BRC5ARIsAALPIlWiPc4O8LfKTUo9A2932tLOMTkar8QLHo2D2l1xdYVfXg_qCFGVYEUaAkZIEALw_wcB
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the only fluid I found that I could run in a shared hot/cold loop that went that low was HC-50 from Dynalene.
another solution is to use vacuum to insulate your columns, then use hot water to heat them. you blow out the hot water and pull vacuum again when you’re ready to repack the columns.
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We have silicon Caldera Fluid it supports -50C to +200C at labcradle.com
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Beware the viscosity of most of those wide range heat transfer fluids. Your pump choice may be impacted substantially by it.
If you do use an alcohol and you’re heating it with a resistance heater, you would do wisely to consider what safeties you use. It might be worth using a BPHE and separate heating system so that you don’t risk a failed element causing a very big problem.
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