Sciencemadness Discussion Board

heating element for water bath

chemrox - 17-2-2008 at 18:13

I need a steam bath and have no steam lines in the bldg. I was thinking of an apparatus I coild make if I had an element that would maintain water at at it's bp. I haven't found one yet and request help for that acquisition.
Thanks,
CRX

Twospoons - 17-2-2008 at 18:33

Sounds like an electric jug with the lid off, to me.

MagicJigPipe - 17-2-2008 at 21:00

The water should remain at it's boiling point no matter what you use. Do you plan on keeping the water under pressure and holding it below it's boiling point at 100C? My water always stays at around 100C no matter how much heat is applied. Suggestions: Electric or gas stovetop, bunsen burner, hotplate, crockpot, infrared light bulb, microwave (superheating can occur I believe). Pretty much any heat source I suppose.

Or maybe I don't fully understand your question.

The_Davster - 17-2-2008 at 21:29

Boiling water is always at 100C at standard pressure. You can have whatever element you want, and the water will be at 100, and as long as the element is completly submerged, the steam will be at 100C as well.

If I was doing what you are, I would simply modify a kettle by removing the thermostat so it is on as long as it is plugged in, and seal it up with an insulated tube leading out to carry steam wherever.

not_important - 17-2-2008 at 23:24

Take those suggestions, run the boiler somewhat lower than the steam bath, and run the condensate back into the boiler. Add a float valve or 'burp flask' reservoir to help keep the boiler filled, too.

Make sure it has a thermo-cutout switch, and perhaps a water level sensor.

bfesser - 18-2-2008 at 06:09

You could use one of those automotive metal oil funnels as a steam cone, perhaps.

leu - 18-2-2008 at 11:31

Locate a source for a Wagner Power Steamer Model 705 which is sold for removing wallpaper and buy as many as you need :P

Intergalactic_Captain - 18-2-2008 at 12:54

Try looking for a hot-water heater element. I used to use one in my (less than legal) still, and depending on how much heat you need they're quite good for the price. The one I used was a single-temperature, 1500W, 120V element, run through a dimmer switch to control the temperature. Very hot very fast, and decent control with the dimmer. The only problem is that due to their design, they must be submerged continually when in use, otherwise a hot-spot can develop and burn out the element. That's why I said I used to use one - I was distilling an unfiltered corn mash one day and a kernel stuck to the element, dried out, caused a hot-spot and burned out the element...I now use a heating element from an electric oven - They're designed to run dry, but can take a hell of a lot more abuse than one would think.

Another option, if you just want steam, is to drop an extension cord in a bucket of water. A while back, I made a humidifier out of a 5-gallon bucket full of water with two floating copper electrodes at ~2" spacing and 120V...One would expect electrolysis to occur, but at that voltage it simply boils the water. Rediculously stupid and will probably short out your breakers/fuses the first time, but it actually works.

smuv - 18-2-2008 at 13:15

Are you running the oven element submerged? How is it mounted in your still pot?

Also, while of course you know your still better than I, it seems a little far fetched to me that a small corn kernel would allow the element to overheat that much. Even if that spot got to 200c which is an astounding 100 degree temperature difference, I doubt the heating element would be fried. I have taken a submersible +1KW element gleaned from a 'Persian tea urn' (can't remember what they are called) and heated it to a dull orange heat in open air for some time without any harm (I was attempting to make a very improvised hotplate). I think it is very possible that your element died for another reason.

[Edited on 18-2-2008 by smuv]

Intergalactic_Captain - 18-2-2008 at 13:24

Yes, my oven element is submerged... And different elements can take different types of abuse. The ones in electric teapots can take a higher temperature before they burn out - This is a result of the intended market - You don't put an element that burns out that easily in something that is less likely to be full when it's used. Not sure that made any sense, but water heater elements are designed to be run continously submerged, while teapot elements are designed for different levels of submersion.

If I still had the element floating around, I'd post a picture of the hole that burned through. For some reason, a pinhole leak is enough to burn out the internal element. Imagine a copper pipe filled with a high-temp insulator, with a nichrome element in the middle...In reality, it's probably not nichrome, but an autopsy of the element proved that this was the design. Don't believe me? Go pick up a water-heater element and plug it in dry - It'll probably last 5 seconds and go up in smoke. I'm not entirely sure why submersion is enough to keep them "cool," but I can attest that it is absolutely necessary. Also, remember that my element was 1500 watts - A weaker element may last longer unsubmerged.

MagicJigPipe - 18-2-2008 at 19:30

Quote:
I'm not entirely sure why submersion is enough to keep them "cool,"


Really? The heat from the element is transferred into the liquid which, in turn, boils and releases vapor. The heat from the element is essentially transferred from the element to the condenser water via the condensation of this vapor.

Therefore, in theory, the element cannot become hotter than the boiling point of the liquid in which it is submerged. Of course, there are some variables that can change this.

smuv - 18-2-2008 at 20:09

While I do find it hard to believe a tiny corn kernel could kill an element, if it actually developed a hole...I have to give your conclusion merit. What I can't wrap my mind around is that, most of the element is still submerged; its like trying to solder a copper pipe when half of it is in a bath of water (it requires a lot of heat!).

All this talk of element failure reminds me of when my element (this time a non-submersible) developed a hole and oozed out molten metal as I was distilling ca 1 gallon of an ether/heptane mixture. That one really made me sweat.

-jeffB - 19-2-2008 at 08:31

Quote:
Originally posted by Intergalactic_Captain
Another option, if you just want steam, is to drop an extension cord in a bucket of water. A while back, I made a humidifier out of a 5-gallon bucket full of water with two floating copper electrodes at ~2" spacing and 120V...One would expect electrolysis to occur, but at that voltage it simply boils the water. Rediculously stupid and will probably short out your breakers/fuses the first time, but it actually works.


Passing 50-60Hz A/C through water isn't going to accomplish much electrolysis. I'm unsure of the mechanisms or rates, but by switching poles that quickly you're not giving the anions and cations much time to segregate.

Many decades ago we had a steam humidifier that was set up sort of like a Kipp gas-generator. There was a wide-mouth glass jar, fitted with a cap that held a hollow Bakelite cylinder with a small intake at the bottom, a steam outlet at the top, and two bare electrodes running the length of the cylinder. When you plugged it in, the water between the electrodes got hot and eventually boiled. Steam built up enough to force the level in the cylinder down, which reduced the rate of steam generation. It was actually a pretty cool self-regulating setup -- dead simple, inherently safe (if the water ran too low, current stopped flowing), and efficient (the reservoir got hot, but most of the power went into making steam). If I ever want to make a steam source for steam distillation or whatever, I might use the same approach.

Intergalactic_Captain - 19-2-2008 at 10:09

Wow - That's pretty simple...I think I might have to build one of those and find an excuse to use it.

What I meant by the electrolysis thing is that there was NO electrolysis whatsoever. Or, if there was, the component atoms reacted back to water in the process...I did not detect the slightest trace of hydrogen or oxygen when I ran it. I was 12 at the time, so my memory may be playing tricks on me, but I think I would remember a oxy-hydro explosion...

-jeffB - 19-2-2008 at 11:28

Quote:
Originally posted by Intergalactic_Captain
What I meant by the electrolysis thing is that there was NO electrolysis whatsoever. Or, if there was, the component atoms reacted back to water in the process...I did not detect the slightest trace of hydrogen or oxygen when I ran it. I was 12 at the time, so my memory may be playing tricks on me, but I think I would remember a oxy-hydro explosion...


When I ran it without the cover, as I recall, no bubbles appeared at all until the water was starting to boil. I don't know how long it takes hydrogen or oxygen to collect and dimerize at an electrode, but if it's more than 1/120 of a second, it'll get driven away before it can bubble out.

chemrox - 19-2-2008 at 21:38

It would be ideal if the device boiled water vigorously and made a nice had of steam over an area appropriate for heating the lower half of a 3L rb. A lot of good ideas here. I hope this clarification yields a few more. Seems like a deep fat fryer might do the job.