Imagine a device which consists of 2 nested pipes - a pipe inside of a pipe. The inner pipe has a fuel/oil burner at the bottom of it, able to draw in air from below. The bottom end of the outer pipe is lower than that of the inner pipe. The top end of the inner pipe vents out into the air. The gap between the inner and outer pipe is sealed at the top end. There is however a spout (like a teapot spout?) which protrudes from the upper portion of the outer pipe.
Lighting the burner results in a thermosiphon. Air will be sucked in from the bottom end (inlet), and will leave via the top. But while the smoke will exit from the central pipe orifice at the top, what emerges from the spout will be clean smoke-free warm air. That warm air is coming out of the spout due to thermosiphon effect, with air in the outer pipe being warmed by the inner pipe, creating an updraft, after being drawn in through the bottom inlet.
Imagine this contraption hanging by its spout off the crack of your slightly open car window, to send in warm air into your car, while you're stranded in the cold weather due to a breakdown. Or else, imagine similarly heating your tent while camping, by positioning this contraption just outside your tent, and having the spout poke in through some tent flap.
The goal of this portable device is to efficiently provide fresh warm air into some interior compartment via fuel burning, without forcing you to inhale smoke as well. Otherwise, people do go camping in hot tents equipped with interior stoves for heating, but there's always the danger of smoke inhalation from the burning fuel in the stove, so that carbon monoxide detectors are often recommended for those situations.-- sanman, Jan 28 2021 Heating Tent With Torch & Thermosiphon https://www.youtube...watch?v=QeHGDr81XwM [sanman, Jan 28 2021] Franklin Stove https://en.wikipedi...wiki/Franklin_stove [sanman, Jan 29 2021] 2021 Texas Ice Storm https://www.youtube...watch?v=M-l1RJk67N8 [sanman, Feb 23 2021] One of the most ingenious heating devices I ever saw was in a rustic rural cottage in France, it was a cast iron grate which stood in the fireplace and which you lit a fire on as usual. But the iron grate was actually a serpentine hollow tube, with nozzle fittings at each side. On the front side was attached a tube that acted as an outlet nozzle pointed into the room, and on the back side was a hose fitting which ran to an electric blower. Cold air blown into the device came out the nozzle as a lovely stream of warm air which heated the entire building up pretty quickly from a small smouldering fire that looked utterly inadequate.-- pocmloc, Jan 28 2021 // looked utterly inadequate. //
Ah, the "Keir Starmer" look ...
[+] for the idea, although wrapping the outer tube in an insulating material - such as blue asbestos - would improve it considerably.-- 8th of 7, Jan 28 2021 Without liquid, it's not really a thermosyphon, more a form of facilitated convection. You'd get more efficiency if you could power the flow in the reverse direction for a countercurrent setup... possibly more convenience too, since it's nice to have war air down low.-- bs0u0155, Jan 28 2021 You might want the bottom of the outer pipe higher than the inner pipe, otherwise the 2 pipes are drawing air from the same direction (inner sucks from the air already contained by the outer) which could be detrimental for one or the other (losing airflow to your burner, or less flow getting heated). Outer higher lets it draw from "outside" while the inner draws from "below" (more-or- less...). //Cat-fights, dog-fights...// Things get interesting when it's cat vs. (small) dog... since cats are so much more powerful (per kg). <anecdote> (Long story short) my cat & my flatmates Papillon dog were playfighting (they grew up together from very young); my cat performed a move a WWE wrestler would be proud of, diving over then rolling under the dog then launching it a metre or so, airborne, across the lounge. I wish I was filming it... </a>-- neutrinos_shadow, Jan 28 2021 to pocmloc: regarding your description of the fireplace siphon heater in the French cottage, I've just added a link to the "Franklin Stove", which was invented by Benjamin Franklin. Apparently it has some kind of baffle designed to siphon air and output it into a room.-- sanman, Jan 29 2021 Looking at what's been happening in Texas, it seems like my idea suggestion was quite timely. Going forward, if this type of product could be designed and built, it might have many takers. I was reading about people who've lost their lives in this terrible Texas storm tragedy -- people who died from carbon monoxide poisoning while trying to keep warm in their car, a young child who went to sleep and never woke up because they died of hypothermia. The concept being discussed here may sound primitive and basic, but in certain circumstances, the fundamentals are what we need to hang onto life. (Added another link for reference)-- sanman, Feb 23 2021 A thought: you would also want the air supply to come from "outside". Probably the "fresh" air (for breathing) but I haven't decided...-- neutrinos_shadow, Feb 23 2021 @neutrinos shadow: Well, that's the entire point of it. Your siphon is sucking in fresh air from the bottom of the device, which could be hanging from the outside of your car window, or hanging from the outside of a tent flap.-- sanman, Feb 24 2021 Ah... for some reason I was visualising the device INSIDE, with the smoke exhausting outside (which would need other pipework). But (now I read it more carefully) with the device OUTSIDE, only the clean hot air goes in. Makes more sense (except when you need to feed the fire...). (More thinking...) with the burner "outside", you lose the direct heating effects (relying only on the air heating). Have the burner inside, drawing air from inside & exhausting outside. Fresh air from outside goes through the heating chamber to inside (driven by both thermosiphon & the fact that the burner is sucking the air out of the space). 2 pipes but more heat, & better to control the burner.-- neutrinos_shadow, Feb 24 2021 random, halfbakery