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Fyndium
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[*] posted on 29-7-2021 at 09:51
Heating bath agitation and temp control?


How to agitate water heating bath at 60C? Do submersible pond pumps stand up to that temp? I use those pumps at lower temps with good results, especially when cooling down a finished reaction when the bath water is replaced with cool water, but they might fail at too hot water. Max temps are not available, as this sort of use is unheard of. Using additional overhead stirrer sounds a bit too heavy solution, but not out of the question. Bubbler agitation with air pump could work, but it also multiplies the evaporation rate, unless the bath is enclosed. The goal here is to sustain a stable bath temp up to 48 hours or more.

Also, do ordinary thermostats from eBay work with immersible water heaters?
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Triflic Acid
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[*] posted on 29-7-2021 at 10:10


Well, for the first question, I would recommend an aquarium air bubbler at a low flow rate. As long as your tubing survives the temp, the actual electronics are always kept at room temp. And what do you mean that max temperature use is unheard off? I thought everyone put aquarium pumps in their tea kettles :P

[Edited on 29-7-2021 by Triflic Acid]




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[*] posted on 29-7-2021 at 13:41


It's hard to picture your setup. I'm guessing to simply use a hot plate/mag stirrer won't work in this type of situations? I'm a little confused haha

Without fully understanding what your restrictions are, I have a few ideas off the top of my head. You could use a larger container for the heating bath and buy something called a "sous vide". It's using for cooking but they clip onto the side of containers and have a programmable screen for keeping the set temperature stable. I believe most of them also cause agitation in some way to circulate the water in the container you clip it onto. It submerges slightly into the water. I've seen people use them before. I actually have one but I've never used it yet.

I think if you aren't able to use a hot plate stirrer in this situation, maybe buying a "sous vide" would substitute.

Maybe you could also look into a temperature controlled sonicator. You can get them pretty cheap on ebay and they work very well. I bought an old one that has a digital screen on it and you can set the frequency of the sonication.

I can't tell if I'm missing the point here or I'm way off track with what you're trying to do. Does any of this seem viable with what you're up to? I honestly think a heated sonicator would be a great option, but maybe this won't suit your application.
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macckone
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[*] posted on 29-7-2021 at 15:36


sous vide:
https://www.amazon.com/Monoprice-Sous-Vide-Immersion-Cooker/...

It is basically two devices in one.
a hand blender: https://www.amazon.com/OXA-Smart-Powerful-Immersion-Blender/...
and a heater: https://www.amazon.com/Instant-Immersion-Electric-Portable-R...
with a thermostat

The one I posted is 800W, which is generally sufficient for non-distillation applications.
Down side is they usually are limited to 90 or 95C.
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Fyndium
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[*] posted on 30-7-2021 at 12:05


Sous vide immerser sounds like the perfect solution. Thanks for that a lot! The sous vide ready vessels are restricted of shape and size, but using own bath vessel allows for perfect configuration. 800W should be enough, if the bath vessel is thermally insulated even if it's larger, and it circulates the water. For upkeeping temps up to 90C I have used ikea induction plates, and I have to alter between stages 2 and 3, which are 250 ja 400W, respectively, so shooting constant 800W of heat will actually boil a kettle of water pretty quickly. The purpose is to have a bath that principally buffers reaction temperature to desired temp, whether the reaction is exothermic, neutral or endothermic, within temp range of 40-100C. If the immerser had a cooling mechanism too, it would be perfect. :D Now, the immerser could likely be used as stirrer only, by using external cooling or heating source when needed.

For the record, I have permanently moved away from magstirs. They are unreliable, lack range and heating and stirring power, restrict the bath options very significantly, basically to glass vessels of minimal size that the heating element usually can not sustain or it will burn out quickly, and are prone to failure upon slightest solids appearance, and now that I tested that overhead work under vacuum as well, the final restriction lifted. Even the cheapest of overheads allow for very effective agitation of even the more solids containing reactions under all circumstances.

Effective agitation of bath fluid at least multiplies the heating or cooling power. I have been able to run exothermic addition reactions much faster when I have immersed an aquarium pump, and also when cooling reactions down, a hot water layer will quickly settle around a flask, stalling the thermal gradient, but strong stirring keeps the liquid at constant heat transfer, and temps come down at least 2-4 times faster, if not even more. From 90C to NTP it won't take too many minutes when replacing the bath water twice or thrice with new, 10C water.

Someone here had a signature stating that single most important vector at reaction is effective stirring. I'm beginning to believe in that.
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[*] posted on 30-7-2021 at 12:28


Looks like the aquarium heating sticks I use to warm the water bath for yeast based reactions.
Those just cost a third or so of that, but they are usually "restricted" to a bit over 30°, I mean, you don't want to cook your fish... but I'm sure someone technophilic enough could manipulate them easily and simply increase the possible temperature by a bit.
They can do that, they just shouldn't.

I know I had such a device malfunctioning, and had to keep my fish in buckets for two days, large ones even.
I think it reached over 40° and a few of the fish even died.
So it is definitely possible to crank them up if you know what you're doing.
The internal thermostat probably won't keep up with this, but thats what thermometers are for.

Of course, or pay thrice as much and buy the sous vide instead.
I would choose the latter, but technically I'm quite illiterate.


Quote:

Someone here had a signature stating that single most important vector at reaction is effective stirring. I'm beginning to believe in that.

Nicodem, I think... or at least, the person has that quote from him in the signature :D
Its definitely true though.

[Edited on 30-7-2021 by karlos³]
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Fyndium
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[*] posted on 30-7-2021 at 12:55


I ordered a 1500w 220V immersion heater just in case.

Personally, if I'm not into that specific business of converting fish cooking sticks to heat above 30C, I will just buy a thing that does the job. I have had my fair share of sub-sub-sub-projects, and after procrastinating few years and ordering more and more all kinds of little trinkets from eBay and wait 4-8 weeks to get my projects one step further (or fail for good) and never getting to actually do the real thing, which is chemistry and reactions and synthesis, I just decided to invest the money needed to get good equipment designed for the very job I want them to do, and carry on with my main hobby. Get a good insulated heating bath vessel, get an immersion heater stirrer with good thermostat control, get a 4-neck rbf with all the required additional glassware like droppers, stillheads, thermowells etc and a stirrer adapter, and get an overhead stirrer with teflon paddle and a flexible axial mount to make it run vibration free. With this setup, I can trust it to work when I want to do some reactions, and expect it to run 48 hours if necessary. :cool:

No any means to offend anyone who wants to configure equipment and DIY. I find it fascinating, but I don't have unlimited time so I want to use it as efficiently as possible. I've been able to advance in my chemistry skills this last year more than the prior 10 combined, when I was just able to fully focus on actual chemistry, not making sure all the tapes and screws held together. When I can confidently say that I can design and run a synthesis based on basic data and end up with desired substance in pure, recrystallized form, I have achieved what I dreamed of.
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[*] posted on 30-7-2021 at 13:07


Absolutely understandable and I would have gone for macckones idea too :D

It might be an interesting idea for someone else though, so I posted it anways.
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[*] posted on 12-8-2021 at 10:19


So I got my immersion heater recently. Based on first test it seems like the best invention after overhead stirrer. It can be clamped on any vessel that can withstand the required temp, it keeps temp at 0.1C accuracy between 0-100C with 1500W max power and it stirs the water decently and has max timer of 99h with max 99h delay setting. This was the more expensive one, but the cheapest ones go for 20-40 bucks.

I'm planning on making a vessel from polyurethane sheets, same stuff that deschem&co uses to ship their glass, because it is extremely good thermal insulator and is stiff and very cheap, a big sheet of 1.2x0.5m and like costs up from 5 bucks, bigger sheets less per sq m2. When a lid with necessary holes for reactors and apparatus cut, the power needed to keep up the desired temp significantly decreases, compared to open vessel, that can require significant horsepower to keep up the heat. It works both ways, a highly efficient cooling bath can be directly adapted, for which an ordinary aquarium pump suffices for circulating the coolant body.

It can be easily cut to desired dimensions and assembled with glue and reinforced with tape, and if necessary, some rigid material to withstand larger liquid bodies. Placing two or more of thick plastic bags into it will make it waterproof. Such vessel is also easy to adapt a drain valve to the bottom, by simply punching a hole and screwing one tight, with backing plate and some silicone caulk if necessary. With this, when reaction is complete, the bath can be immediately drained from hot water and replaced with cold water, effectively stirred, so the reaction temp can be brought down in fast order.
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[*] posted on 12-8-2021 at 23:55


Quote: Originally posted by Fyndium  
So I got my immersion heater recently. Based on first test it seems like the best invention after overhead stirrer. It can be clamped on any vessel that can withstand the required temp, it keeps temp at 0.1C accuracy between 0-100C with 1500W max power and it stirs the water decently and has max timer of 99h with max 99h delay setting. This was the more expensive one, but the cheapest ones go for 20-40 bucks.

I'm planning on making a vessel from polyurethane sheets, same stuff that deschem&co uses to ship their glass, because it is extremely good thermal insulator and is stiff and very cheap, a big sheet of 1.2x0.5m and like costs up from 5 bucks, bigger sheets less per sq m2. When a lid with necessary holes for reactors and apparatus cut, the power needed to keep up the desired temp significantly decreases, compared to open vessel, that can require significant horsepower to keep up the heat. It works both ways, a highly efficient cooling bath can be directly adapted, for which an ordinary aquarium pump suffices for circulating the coolant body.

It can be easily cut to desired dimensions and assembled with glue and reinforced with tape, and if necessary, some rigid material to withstand larger liquid bodies. Placing two or more of thick plastic bags into it will make it waterproof. Such vessel is also easy to adapt a drain valve to the bottom, by simply punching a hole and screwing one tight, with backing plate and some silicone caulk if necessary. With this, when reaction is complete, the bath can be immediately drained from hot water and replaced with cold water, effectively stirred, so the reaction temp can be brought down in fast order.


I really like that idea, would you be so kind as to document the building and operation of such a device in it's own thread?




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Fyndium
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[*] posted on 13-8-2021 at 06:41


I get my workspace by the fall, so if you are patient, I might actually give some details. The drain valve I was gonna use a simple sink discharge outlet, since they fit directly to a suitable sized hole without any improvisation.

[Edited on 13-8-2021 by Fyndium]
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[*] posted on 13-8-2021 at 07:40


Styrofoam/expanded polystyrene insulated food boxes are cheap, waterproof and excellent insulators,
great for diy water baths, ice-water to almost boiling.




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[*] posted on 13-8-2021 at 08:37


You could get a plastic bucket, cut pail or any resistant container and then use either foam spray, plastic sheets (deschem packing type) or ceramic oven insulation blankets to make the insulation on the outside of the pail/container.
A foam insulated pail like that can handle chemicals pretty well and have good thermal insulation.
The sous vide cooking devices have caught my interest too, but i would like a bit higher temps.
They seem quite nice though, heating with regulation and stirrer.
If the sous vide doesnt work there must be pumps that can withstand higher temps but are probably expensive.
Maybe a pump from a vehicle or other device that pumps hot liquid can be used.

I have bought this 250ml high-pressure thermal synthesis reactor that i would like to make a heater or heating block for.
I have thought about putting it into a heated oil-bath or in a oven but a aluminium heating block would be nice and no hot oil.
I could put several cartridge heaters in an aluminium block and let a PID temp controller with a SSR and temp probe heat the aluminium block and the reactor.
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[*] posted on 13-8-2021 at 13:05


You will have some challenge finding non-metallic vessels that handle +100C. Hence, for any operations above 100C, I will just use a large SS kettle with induction plate, which can easily handle temps to 200C and above, necessitating you have suitable bath media for it. Immersible heaters with thermostat controller could deliver these temps, if induction plate would not be an option. If you are restricted to sub-1000mL flasks, you could do with ordinary good grade stirplate, too. Sous-vide delivers out-of-box-all-inclusive appliance for 0-100C baths and is designed to run for two days straight, so it's the ideal appliance for reliable reaction condition control.

I originally looked into having a separate box, insulation and other stuff, but as I'm a keen user of Occam's Razor, I want to find the ultimate simple and idiot-proof solution, and as I have already used deschem boxes for cryogenic operations successfully, they have proven to be very effective. The PU sheet is rigid, easy to cut and assemble, cheap and has one of the highest thermal insulation values of all insulating media.
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