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Author Topic: Are there precision heating/cooling elements for chemical solutions?  (Read 1909 times)

Offline curious_mind

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Hello all,
 I'm simply wondering if there is a device (such as a stove) that can reliably keep solutions between two temperatures (ex. 10-20 deg. C) and can be set for different temp. ranges on the fly. My gut tells me such a thing exists, but i cant find info on one anywhere. I couldnt find an equipment section so i posted in chemistry since chemists would be most likely to have experience with such apparatus. Thanks.
« Last Edit: 23/12/2013 09:40:09 by chris »


 

Offline SorryDnoodle

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Re: Precise heating/cooling element for sensitive solutions
« Reply #1 on: 17/12/2013 22:56:58 »
Not sure what you are looking for but I looked around and found this site that sells temperature controlled hot plates, have a look.

https://www.spectrumchemical.com/OA_HTML/Equipment_Burners-Hot-Plates-Heaters_Hot-Plates_Heat-Only.jsp?minisite=10020&respid=22372

By the way, what are you using one for?
 

Offline chiralSPO

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Re: Precise heating/cooling element for sensitive solutions
« Reply #2 on: 18/12/2013 19:42:22 »
There are many devices that can be used for temperature control. Selection of device depends on many factors, but the most important are:
what temperature are you trying to maintain? (55 C, 37 C, 130 C, etc.)
how much error can be tolerated? (10C, 1, 0.001???)
how big of an experiment do you need to temperature control?
how much are you willing to spend?

Answers to the first 3 questions will dictate the last to a great extent, but there is always some wiggle room.
 

Offline Bored chemist

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Re: Precise heating/cooling element for sensitive solutions
« Reply #3 on: 19/12/2013 10:23:24 »
For general lab use there are these sorts of things
http://www.coleparmer.com/buy/product/65954-6-liter-standard-digital-controller-heated-circulating-bath-120vac.html
Other manufacturers also produce similar products.
you can also get versions that cool the material below ambient, those cost rather more.
 

Offline wolfekeeper

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Re: Precise heating/cooling element for sensitive solutions
« Reply #4 on: 22/12/2013 01:42:22 »
Yes, for kitchen use check out 'sous vide' controllers. They can keep a container full of water stable to under a degree or so.

I designed, built the hardware and coded a microcontroller to do this.

The tricky bit was dealing with the delay; there's a long delay between turning the heat on and the temperature beginning to rise at the temperature sensor; and then you overshoot; and there's an even longer delay before the temperature comes back down again. Also, tempering chocolate, really easy.

Industrial processes use PI or PID controllers, and you can tune them to not overshoot, but they're fiddly to set up.

You can bag up and cook some steaks this way; they take about 16 hours to cook, but the results can be amazingly tender (although occasionally if you overdo it the steak turns to mush!). Also you can do interesting things with eggs, and many skillful cooking processes requiring very careful temperature control, like making custard, tempering chocolate, and excellent scrambled egg become trivial.
« Last Edit: 22/12/2013 01:45:45 by wolfekeeper »
 

Offline syhprum

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Re: Precise heating/cooling element for sensitive solutions
« Reply #5 on: 22/12/2013 15:29:42 »
As you say the time delay is a problem I looked into this in the forties when I had the job of designing a temperature controlled ducking bath for turkey plucking and although I did not actually manufacture it I worked out that the best solution would be to have a continuous circulating system with a reservoir of water at the correct temperature and pump it into the bath as it cooled.
I believe the problem is something like that of balancing an inverted broom on a computer controlled trolley , software exists to do this and it is fascinating to watch.
« Last Edit: 22/12/2013 15:34:21 by syhprum »
 

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Re: Precise heating/cooling element for sensitive solutions
« Reply #5 on: 22/12/2013 15:29:42 »

 

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