Spark arrester and heat exchanger?

[jamieS]

At WCS, there were a few Snowtrekker tents that had an expanded section of their stove pipe that was on the inside of the tent. It was described as a spark arrester and heat exchanger. It sort of looked like the stove pipe was about 4" and this thing was a 1 1/2 foot section of 6"inch pipe.

Does anybody know what I'm describing? Where do you buy such a thing?

[timdaman]

Are you describing a stack robber?

https://www.kni-co.com/index.php?route=product/product&product_id=95

I have seen pictures of ones that are round too. I have never seen one in person. I think the idea is there is a bunch of metal surface area the smoke dwells in dumping heat and cooling off the sparks before it continues up the stack. .

I have no idea how well they work.

[jamieS]

The Stack Robber makes sense since it's also a Knico product like the standard snowtrekker stove... but I swear there was something more like this except the exterior pipe was shiny like stainless steel:

[timdaman]

That looks a lot like a tent protector.

https://www.google.com/search?q=tent+stove+protector

Again, never had one but from what I can tell they create a free flowing air gap between the stove pipe and the outside surface. Tube inside of tube with a gap between. The air gap keeps the outside face cooler and prevents the stove from melting or burning the tent.

When I think of preventing sparks I think of
1. Reducing their production, i.e. don't burn paper.
2. Slow down the movement of smoke so the sparks have more time to complete burning. Baffles(by making the smoke make hard turns) and lower damper settings(by resisting the flow) help do this.
3. Blocking them by "filter"ing them out which leads to them, again, getting completely burnt. This only works when the "filter" is close enough to the fire to keep very hot.
4. Same as Community but with the filter on the far(cold) end of the pipe. I find at that location, yes, they reduce sparks but tend foul up and block flow creating other problems.

I don't see how what you pictured (or a tent protector) would be particularly effective against sparks. I see nothing to slow the movement of the smoke nor any sign of "filter"ing.
What I suspect is that, if these are completely in the tent, they are there to prevent burns by creating the air gap. The gaps allows cool air to flow in to keep the outside cool. They conserve a bit of the heat in their convection.

[MRaske]

Don Kevilus @ Four Dog stoves has made a heat exchanger and it is likely what you were seeing at WCS. I don't see them on his website currently. I really don't know a lot about them. We have used one the last couple of years though

Hoping Lonelake or someone more knowledgeable that I will jump in here to tell you how it works.

Here is a pic of a happy camper and the exchanger that we use.

[jamieS]

Aha, that's it! Thanks MRaske!

[jamieS]

Just following up on this one... does anyone have an idea on how it works? I'm trying to imagine the cross section and how it might function as a heat exchanger? Seems different than the heat exchangers with baffles/multiple tubes/etc.

Google got me this, but that's about it: Problem solved, Fourdog Turbo Spark arrester, draw assist and heat exchanger. Proto type. | By Four Dog Stove | Facebook

[Scoutergriz]

Just following up on this one... does anyone have an idea on how it works? I'm trying to imagine the cross section and how it might function as a heat exchanger? Seems different than the heat exchangers with baffles/multiple tubes/etc.

Google got me this, but that's about it: Problem solved, Fourdog Turbo Spark arrester, draw assist and heat exchanger. Proto type. | By Four Dog Stove | Facebook

I suspect it works a lot like an old device I saw in a cabin years ago- the inner pipe has a slight restriction in the bottom and openings just above, along with openings at the top on the outer pipe allowing it to draw in fresh air which combines with the venturi effect to produce an "afterburner" like effect, burning off the exhaust gasses and scavenging the extra heat produced.

[jamieS]

Ah, so the goal is mostly complete combustion, but the thin wall of the outer pipe provides additional heat exchange and the blast-furnace effect eliminates all the sparks before they get up the chimney. Neat!! This seems like a great way to reduce sparks.

[jamieS]

Found this while surfing... good explanation of a commercial spark arrester: Spark Traps - The Real Spark Trap from US Duct - YouTube

[Heavy Duty]

I've got one from fourdog. Their design is ingenious, the larger diameter, slows down the velocity without restriction, the "fan" in the center creates a vortex. then there are air holes to add fresh oxygen, with all of that will act like a combustion chamber in a jet engine when the air, turbulent (fuel) wood stove gas get necked down into the stove pipe.

This thing glows red hot and the pipe above it is not.