Propane ‘stove’

dunno how practical it could be… But you probably need to increase the surface area of contact between that hot tube and the water, by maybe coiling it up a few times in the pot.

Expanding on the idea, this could be like a propane fired back-country boiler. It'd basically end up as a mini version of the hot water heater in our houses. Burner on bottom, many small diameter tubes going up through the water, etc. I could see it as being pretty efficient, but might be difficult and expensive to make, as well and hard to make light enough to satisfy this crowd.

BM

I worked with my Dad on his appliance repair business and then we owned appliance store and I was in the industry years with 18 years in between when I was in the air force and sold athletic shoes. I did many change outs of jets and air adjustment going into the burner for converting natural gas appliances to propane.

Basically your not get enough air in the burner tube to heat water to keep the flame lit.

I have a question is this to heat water for food or is it a experiment on much larger backwoods large capacity water heater for bathing in?

If it for food you can't beat our stoves we have right now.

If it for water heater most are just like a stove with a large burner ring about 8 inches to 12 inches in diameter on the bottom under the large tank attached to a regulator and large propane tank for fuel. The regulator adjust the flame to how hot the water you want in the tank.

I am not familiar how tank less gas water heater works. here's a link to how both types water heaters work hope this helps.
http://en.wikipedia.org/wiki/Water_heating

Have fun
Terry

Propane canister has higher pressure than butane or iso-butane, so the canister needs to be much thicker – heavier – not practical for a lightweight backpacking stove.

For example, a propane bottle for soldering plumbing pipes is very heavy.

Thanks for insights, for Terry especially. I maybe need to try some other tube diameters to get more air in.

This wasn't specially a test for small cook stove or large bathing tub. It's just a test of the idea in general. Pro's & cons I have in mind for cook stove would be:
+ ability to use a food thermos jug as a winter kettle
+ no more falling cookpots, since pot rests on the ground
+ plastic cookpot? (well, maybe not an advantage)
+ no soot on the pot (with LPG hardly a problem)
+ no need for windscreen
+ it's fun to test everything weird
– it's certainly heavier than canister top stoves
– smaller heated surface area probably means lower fuel efficiency
– can't use for much else than heating liquids

For wilderness bathtub use it could be cool. But maybe not as easy as heating water in your kettle and pouring it to tub.

Alpo,
That is really neat idea for a gas internal stove element to boil water for cooking,so you don't need a wind screen or pot stand. You are really thinking out of the box.

I have a Idea to make the project work experiment with smaller diameter tubing that gas/flame tube to get more oxygen in to keep the flame lit. With smaller jets/holes drilled gas flame tube in the that fits in the large tube you have now. It may work In till you get a stove that boils water.

Another way to make the stove with a center 4cm large diameter stainlees steel stove tube that has vertical stove burner from stove we use now and your breather tubes with the gas line inside.

It would submergible chimney stove that would sit in your pan and the flame would be directed vertical with and lit with a peizo lighter. The flame would be directed up ward and heat the chimney to heat the water.

Be careful and wear leather gloves and face shield when experimenting like this and burn in open area like outside on a cement patio. I speak from experience on the job I turned the gas off to add a gas line for gas clothes dryer when I was about 17 years old on the job.
I was trying to light a hot water heater and it would not light and I would stick my head down their with my Match extension tool to see what was wrong and it lit and blew a flame out like jet engine in my face. Burned off my eyebrows and long hair bangs and hair off my arms it burned a little but I smelled funny with that burned hair smell. The hot water heater stored to much gas when it lit all of sudden.

It's funny I use to play with fire and fire works a lot when I was kid never had a mishap. I have brother who burned a three acre field playing with fire works with his friends and the fire marshal gave hime and his friends a stern waring. I always tease him and tell my nephews they need to "learn how to play with fire safely" and they think that is funny wording.

Have fun with the stove experiment I hope it works it would revolutionize the way we heat water with out creating a forest fire hazard like most stoves do now.
Terry

Alpo,
Here's a simple drawing of the stove
Terry

Noticed a small cheap propane burner (Sievert 884401) at the local hardware store and decided to test it. I used the original jet made for butane/propane mix with the body of Sievert burner, and much smaller diameter heater tube than before.

https://picasaweb.google.com/lh/photo/0nZ5MuRqVq6vKKAjaXq6hIbsAqoXbwEuQaFFz3o40w4?feat=directlink

Result was promising, but not usable yet. I could smell the gas all the time, so obviously only part of the gas was burning. Flame kept burning all the time, even with some blowing to test the effect of wind. It took over 15 minutes to get half a liter of water to almost boil (fish-eyes), but it never got into rolling boil.

You may be able to smell the unburnt gas, but you will not be able to smell the carbon monoxide. LETHAL! DO NOT test this indoors!

Alpo,

This is could be made to work, but there are hurdles to overcome, as you've found out and as I found when I was playing with it on a larger scale.

First: you need enough air to combust the fuel. (More than enough because unburned gas is a clear sign that you're making carbon monoxide. I understand wanting to play inside in the winter – I do, too – but the most enclosed I'd be for this is in my garage with the 8' x 10' door open during any test firings of the stove.) But back to the combustion process: you need more air. You need a way to induce more air flow. Mechanisms include: (1) the momentum imparted by the flow of butane through the jet (that's what moves atmospheric air into and through a BP stove, bunsen burner or your gas-fired kitchen stove). (2) chimney effect of a tall vertical pipe of hot gas that is lighter than the surrounding air. This is how a fireplace get's its air and why you have to "establish a draft" with a small fire or by burning some paper before starting a larger fire. (3) some forced ventilation with a fan.

Also, any of those mechanisms will more air in a larger pipe. Monmentum from the jet works fine when the "pipe" is the size of a room, tent, probably down to about 6", maybe 4". Going to sizes below that and I'd suggest you use chimney effect.

I'd suggest you start playing with the "Backcountry Boiler" or "Kelly Kettle" concept – a larger inner tube (2"-3") with a surrounding water jacket. But with butane instead of wood, you could put HX fins and vortex generators on the inside of the exhaust tube as is done in gas-fired water heaters. And I'd take a page from JetBoil and put a cosy around the outside of the water jacket. The taller you make such an arrangement, the more efficient it will be – more HX area, more energy extracted from the exhuast gases, and more chimney effect. Of course it is less compact and light, so it's a trade-off.

With the bigger set-ups I was playing with, (I was doing backpacking hot tubs for naked college students), the bounancy of the 4" tube gets to be a bother. It has to be air-filled and that displaces a large/heavy volume of water. I did a U-tube like you did, but I think a vertical arrangement is probably easier to make work, water-proof and keep submerged. When you get the basic, vertical chimney and burner working, you can search out a matching, tall, narrow pot.

I have seen some stainless-steel vacuum mugs (for your morning coffee on your way to work) that were tube-in-tube with a void between them. And a similar stainless steel water bottle. They have a vacuum jacket as is, but cut into it and you could have a water jacket. It would be a small water jacket but it would let you test the concept. The size is close to what you want: 2.5-3" inside, and MUCH better than what you've been using. $12 is cheap for water-tight, welded, tube-in-tube stainless steel. You wouldn't be out of the woods yet – there's thermal expansion to consider, so I'd suggest ALWAYS having water in the annular space because you don't want the inner tube at 500F while the outer one is at 70F. But with water in it, the inner tube would stay at 212F and it is designed for that.

Here's a travel mug that appears to be stainless inside and out for $11:

http://www.sierratradingpost.com/stanley-insulated-travel-mug-16-floz-bpa-free~p~3570f/?filterString=search~insulated-mug%2F&colorFamily=01

Cut off the bottom and you have the start of a inner chimney with water jacket.

Interesting concepts. I don’t have David’s engineering background, but I would agree just based on playing with (a lot of) stoves that the issues will be getting sufficient air to the flame, obtaining full combustion, and possible problems with carbon monoxide. With whatever experiments you do, be careful if you smell uncombusted gas. Carbon monoxide is a very serious and lethal problem, but you could also have gas build up in an enclosed space. If you reach the right mix of air and gas and a spark were to occur or the air-gas mixture were to encounter a heat source… Well, you’d at least need a new house. Fuel-air explosions are very, very powerful.

Interestingly, the US Army was working on a hot water heater something like what you’re talking about. I don’t know the current status. Here’s a small photo:

There’s a much better photo on page eight of this PDF: US Army Soldier Systems Center — The Warrior, May-June 2005.

It appears to be a coil with two hoses that clips to a stove. One hose attaches to a water bladder or other source, and the other is a exit hose that would feed into a pot, mug, or other receiving receptacle. I’m not sure how it circulates the water, but it may be heat driven. It could also be gravity driven.

HJ
Adventures In Stoving

You might want to look into what are called "side burners" for homemade gas forges for blacksmithing. They use a long venturi tube to hold and amplify a flame that is plugged into the burning chamber, although in this case you would probably be looking at some kind of heating coil.

This is an example with some data:
http://zoellerforge.com/sidearm.html