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Fulmen
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Using a halogen lamp as a enclosed heater element?
Does anyone have any idea of the maximum operating temperature for tubular (R7S) halogen lamps? I need a small heating element for a boiler, and it
just occurred to me that a halogen lamp is a compact heating element that also put out some light.
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draculic acid69
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Use a lava lamp.boiling flask + heater all in one
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RogueRose
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I'm sure it's well over 212. Is it going to be submerged? I've cut a bunch of these up to use the quartz tube (at least I'm pretty sure it's quartz)
and they can take a blowtorch and then be dunked in water w/o a problem.
As for how hot the element gets itself? I think that would be determined by how much contact it has with the surrounding, air flow mainly, or
possibly liquid if you are careful. I know incandescent are like 99% heat and halogen's are more efficient but not a whole lot, so I suspect you'll
get about 90% of input as heat. So if you have a 1000w bulb, expect about 900w of output as heat, the rest as light, though I'm guessing it's higher
than 900.
As far as temp, I think if you were to wrap it in foil and insulation you could get it probably to melting point of one of the two until failure, if
insulated enough.
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Fulmen
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The idea was to place it in a submerged copper tube. The inside of the tube should probably be painted or stained black to maximize absorption.
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wg48temp9
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The limit on the quartz tube is about 1100C but the molybdenum seals must be kept below 300C or they oxidise and fail, from memory.
I am wg48 but not on my usual pc hence the temp handle.
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Fulmen
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That's useful. According to Wikipedia "weak oxidation of molybdenum starts at 300 °C (572 °F); bulk oxidation occurs at temperatures above 600 °C".
The glass body will of course handle much higher temperatures, Wikipedia lists a temperature of 540°C for a 500W bulb.
[Edited on 14-5-20 by Fulmen]
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Sulaiman
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due to the operating temperature of the filament the lifetime of a lamp will be many many times shorter than the service life of a nichrome heater
CAUTION : Hobby Chemist, not Professional or even Amateur
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RogueRose
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What about using the the elements from a toaster oven. Many of these are quartz tubes as well, I think with nichrome inside. they often have a
frosted/foggy outer shell. There are also standard resistance cooktop elements that are just long and skinny (black).
what about buying a cheap 120v hot water heating element? I know they make them in 120w, 250, 400, 600, 1kw, 1.5kw and they are cheap, I think like
$10-15 for an element. You can probably control it with a dimmer or a speed controller. They sell them on ebay for like $4-8 for a 2000w controller.
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Fulmen
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@Sulaiman: True, but as long as they are dirt cheap and available everywhere I can live with that.
@RougeRose: Toaster ovens just aren't a thing around here, and I don't like to depend on things that take weeks to replace. I'm looking around for
infrared patio heater elements that could fit, but that's not panning out either. And hot water heaters are just to large for this application, even a
standard R7s bulb is longer than I'd like.
[Edited on 15-5-20 by Fulmen]
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draculic acid69
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Are u worried about u.v. destroying any of whatever your making?
I've seen red handwash turn blue just from sitting in the sun.
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RogueRose
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Would any of these work?
https://www.ebay.com/b/cartridge-heater-120v/bn_7024876536
https://www.ebay.com/b/cartridge-heater/bn_7024791228
You could embed them in a copper pipe and seal up each side with something. I've poured molten metal on them (aluminum, zinc, ZA27 zinc-al-copper
alloy, lead, etc) You could fill a pipe with these cartridges and then pour hot metal. Or even high temp silicone.
[Edited on 5-16-2020 by RogueRose]
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Fulmen
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@draculic acid69: Nope, the bulb will be contained in a copper tube.
@RougeRose: Sure, but as always it's yet another thing with a 3 week waiting period. If possible I want OTC components.
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G-Coupled
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That sounds interesting - what was it you were aiming to build when doing that, as a matter of interest?
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RogueRose
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A simple heating element. I started with a billet of aluminum and drilled holes for the cartridges but found it was really difficult to get a tight
fit even with a drill press. I know it is my fault for how I drilled it, but w/o the right tools, it's hard to get a good deep hole that doesn't have
any play in it.
so I decided to try and pour some metal on them and then flatten the surface. I think this could be a decent way to make a hotplate if you can grind
the surface flat enough.
I'd suggest getting the metal a good bit past MP and then also heat the cartridges. Mine get up to about 1880F IIRC, so they get plenty hot to melt Al
if the heat isn't drawn away. But pouring the metal while they are hot allows you to move them a little if you have to. I used wood as a mould and
drilled holes through the side for the wires and also a small recess to hold about 2-3mm of the heater. The wood scorches (use very dry wood!!!) but
it solidifies fast enough to not be a problem. Afterwards I drilled and cut the wood away.
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Fulmen
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Funny thing, I just realized I do have a cartridge heater. But it's stuck in a heating block, and I don't know if I can get it out without destroying
either of them. Besides, where's the fun in that? I've assembled a test vessel, just need a couple of bulbs for the test.
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G-Coupled
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That's cool - how many heating cycles has it withstood so far? Are they costly to purchase, the prefabricated elements of a similar capability/type?
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Fulmen
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Huh. I gotta say I'm slightly surprised, but first impressions are good. 400W bulb, 30+ minutes run time, water's boiling, bulb still shining.
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G-Coupled
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Quote: Originally posted by Fulmen  | | Huh. I gotta say I'm slightly surprised, but first impressions are good. 400W bulb, 30+ minutes run time, water's boiling, bulb still shining.
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That sounds good so far - how'd you have it configured?
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Fulmen
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Rougly like this:
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Fulmen
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Well, it's been 4 hours now and it's still chugging along. I know the bulb isn't properly centered, but that should only increase the thermal load and
I figured a stress test was appropriate.
To be continued.
Update: Another 4 hours today, still working.
[Edited on 19-5-20 by Fulmen]
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Fulmen
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I managed to break the bulb from rough handling after 8 hours, so I'm moving forwards with the project. I'll do another test once the setup has been
improved slightly.
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Fulmen
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I should stress that I blackened the inside of the pipe with a polysulfide-solution. I tried a new setup without it and it melted the solder off the
bulb in less than a minute. Kinda obvious really, but I had to try.
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yobbo II
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https://www.cfs.gov.hk/english/programme/programme_rafs/prog...
https://en.wikipedia.org/wiki/Halogen_oven
ETC ETC
You might be able to get halogen elements in the dumpster. They are sometimes used in those cookers with flat 'glass' tops.
Yob
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Fulmen
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I have never seen anyting like that around. They're just not sold around here.
This helped a lot, but after an hours run the leads came off simply by handling them. I'll see if I can reduce heat transfer further still and perhaps
add some cooling fins on the aluminum plug.
[Edited on 22-5-20 by Fulmen]
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G-Coupled
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That's pretty cool - if you aren't already, you should always ensure that the outside glass/quartz enclosure is spotless of skin grease etc., as this
apparently can cause stress fractures when heating/cooling.
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