Sciencemadness Discussion Board - General Question about heating mantles

General Question about heating mantles

Journey - 12-5-2017 at 18:27

This is probably going to be a dumb question for all the seasoned members here but here it goes. I recently bought a heating mantle for 1000ml flasks. When it arrived I threw my 1000ml flask in it to size it up and found it's not a snug fit. There is quite a lot of open space between the sides of the flask and sides of the mantle fabric. First thought I had was it was wrong sized for 1000ml but a 2000 might fit nice and snug. I brought this up with the seller along with a pic and they came back with that's the way it's supposed to be. This is a unit I bought on AliExpress (China) and has its own power supply all self contained with digital temp settings and readouts. Thought it would be a good starter unit. But I think I'm going to run into problems with it. I have read that one can use sand to make the flask a tighter fit but sand is going to get into the mantle fabric and be messy.
So the question is ... is the mantle supposed to fit snugly around the flask ?
If so will a good quality silca sand do for making better contact or should I use something else like fibreglass ?

Other options I have considered since I ran into this issue are ... get a 2000ml flask and see if that fits better OR get a new mantle with out a containment setup ie. just the plain mantle without an enclosure and make my own holder and use 1 of the 3 variacs I have sitting around here. I was going to buy just a mantle and make my own setup using variac cuz I have 3 of them but thought ah spend a few more bucks and get a factory made unit with it's own power supply. I'm now regretting that I didn't go that way since I am thinking this unit is going to cause problems with no contact to the sides of the flask.

I haven't actually used it yet so I don't know if problems will arise as I just rewired my stove plug to accomodate the 220v power required. I have included an attached image which should give a good idea of the space which is the issue.
Some help will be appreciated.

Journey

[Edited on 13-5-2017 by Journey]

[Edited on 13-5-2017 by Journey]

Magpie - 12-5-2017 at 19:23

That looks good to me. I don't think a larger flask would fit in that space.

I've used mantles like that on small flasks which were for larger flasks and I've always been able to get good heating even with the space gap. Most of the heating was radiant I think.

Fill your flask 1/2 full of water and try it.

[Edited on 13-5-2017 by Magpie]

[Edited on 13-5-2017 by Magpie]

PirateDocBrown - 12-5-2017 at 20:31

You can put some foil, then some sand in there, for smaller flasks. Spreads the heat around a little better.

Journey - 12-5-2017 at 23:52

Thanks for the advice ... I did a trial run with water in a double necked flask which was slightly larger than the single neck and seemed to work ok ... radiant heat. Had the temp probe in the 2nd neck and it seemed to work fine. Lots of smoking though but it was first run ever and to be expected. I still like the idea of the full contact along the sides ... less wasted energy and all. The temp probe worked well save for that it's too short. Have to have the flask nearly full for it to make contact with fluid. Can try the sand fill but sand is going to get into the fiber covering of the mantle fabric and cause messy issues but if that's the way it has to be ... so be it.

Journey - 12-5-2017 at 23:59

Ya was thinking about foil for fill and heat transfer ... less messy than sand. I saw a vid on making yer own heating mantle and he wrapped it tight for whatever size flask he was using but then one would have to do that for all different sized flasks that one is using and buy a number of heating strips and that could get expensive at at least 100 bucks a pop for the strips. I like this idea but the way to hold the mantle was kinda mickey mouse and IMO not very safe for spillage issues. Even though if one has a spill even the best setup isn't going to save you form damaging spills.

I set the temp to 100C and the probe measured about 98 -99 and the water was boiling so it looks like the thing actually works ok given the fact of the space between the sides. Damned Chinese and their radiant heat ! Who do they think are Tesla ?

[Edited on 13-5-2017 by Journey]

[Edited on 13-5-2017 by Journey]

Deathunter88 - 13-5-2017 at 04:16

Quote: Originally posted by Journey

Ya was thinking about foil for fill and heat transfer ... less messy than sand. I saw a vid on making yer own heating mantle and he wrapped it tight for whatever size flask he was using but then one would have to do that for all different sized flasks that one is using and buy a number of heating strips and that could get expensive at at least 100 bucks a pop for the strips. I like this idea but the way to hold the mantle was kinda mickey mouse and IMO not very safe for spillage issues. Even though if one has a spill even the best setup isn't going to save you form damaging spills.

I set the temp to 100C and the probe measured about 98 -99 and the water was boiling so it looks like the thing actually works ok given the fact of the space between the sides. Damned Chinese and their radiant heat ! Who do they think are Tesla ?

[Edited on 13-5-2017 by Journey]

[Edited on 13-5-2017 by Journey]

I wouldn't put sand or foil around the flask, as heating mantles are designed to have a large air gap to ensure even heating/heat distribution. Adding sand/foil to insulate might even have the opposite effect, causing heat buildup within the mantle to the point where it melts. Additionally, scrunched up aluminum foil is a terrible heat conductor due to the air pockets within. If you need something to conduct heat, use a solid block of aluminum.

Magpie - 13-5-2017 at 07:08

I have these mantle sizes: a 100 and a 500ml, and a flattened 500ml. For rbf's (flasks) I have 25, 50, 100, 250, 500, and 1000ml. I don't have any problem heating any of these flasks. I think you are making too big a problem out of this.

I don't use sand or foil in the mantle but will add a fiberglass blanket or foil onto the upper part of the flask if needed.

S.C. Wack - 13-5-2017 at 10:40

Maybe it's the glass...but what you really want to know is the temperature everywhere on the outside of the flask's lower third. I'd want to know what's going on at the very bottom...and maybe the internal construction of this appliance.

I would try .177 BB's...on the fence on lead shot. I might buy little steel shot for something like a 2-l. RBF in a 3-l. mantle.

How does CN glass fit CN mantles? My CN RBF is obviously fatter side by side with US brands. My many US mantles up to 3-l. fits Kimax, Ace, and Pyrex glass like a glove (so, I won't be buying any CN RBF's for them). If there is any airspace, it's a bit at the bottom. A UK mantle has a little wiggle room with US glass, but fits the CN flask perfect at the sides.

[Edited on 13-5-2017 by S.C. Wack]

JJay - 13-5-2017 at 10:56

My US mantle (Glas Col) fits my 3L Chinese RBFs perfectly. One is generic, (I think Reacware?) from Deschem, and the other is GG-17 from Nanshin. I only have one mantle, so I have been thinking trying it with BBs to heat a 1L flask... seems like an excellent idea, especially with mechanical stirring. I have noticed that my two Chinese 1L RBFs are slightly different sizes, with the GG-17 one being slightly larger than the generic.

A few YouTube chemists have used temperature probes in their heating mantles to make sure the glass doesn't get too hot.

Sulaiman - 13-5-2017 at 10:57

Before starting my diy mantle I was considering radiant heating as
it only penetrates a few mm into water.
i.e. water is an excellent i.r. absorber.