Woodstove as evaporator

[PHSINV]

I’m a few years in now and am moving from our gas grill, to my wife’s delight, to another heat source. I like the convenience of propane and just purchased a 367K btu (advertised) 18” propane cooker ($87 from Big Orange). I’m considering using it in a firebrick lined woodstove with a large-enough flat top to hold the pan. If I can elevate the cooker inside the woodstove so it nearly touches the inside top of the stove would the heat transfer be enough for a decent boil? I realize the best case is for the bottom of the pan to directly contact the heat source but thinking this setup might be good enough. Thanks in advance!

[Pdiamond]

You are correct in your one statement that the heat source should be in direct contact with the pan. You will get a much better evaporation rate that way. If there is any way to make this happen I would do it.

[PHSINV]

Thank you pdiamond! I found a video of a guy on YouTube who tried this with less than good results. Then another who used a woodstove and cut out the top so the pan was in direct contact with the heat. I think I know what I’m going to do!

[berkshires]

Thank you pdiamond! I found a video of a guy on YouTube who tried this with less than good results. Then another who used a woodstove and cut out the top so the pan was in direct contact with the heat. I think I know what I’m going to do!
My first arch was a wood stove with the top cut out. Worked fine for a while, but I didn't insulate it, and after a few years it warped beyond the point of usability.

GO

[PHSINV]

Thank you! It occurred to me in the last few days I should insulate it - planning on using ceramic insulation or fire bricks or both.

[wiam]

Bricks don’t insulate.

[DrTimPerkins]

You’ll see that those large BTU propane cookers are very inefficient and the output varies considerably. As they release gas at a high rate the orifice freezes up, slowing down the heat. It’ll then thaw and speed up again, which causes another freeze-up. Dialing it down a bit helps prevent this cycling. Putting up even a modest windscreen will also help the heat transfer efficiency quite a lot. Regardless, be prepared to go through a good bit of propane.

[PHSINV]

Thanks Dr. Tim! I’m going to have it in the woodstove inside my sugar shack, which is in the woods so wind should’ve an issue. Since I’m not relying on a wood fire I’m going to presume I won’t need a stack for draft.

[Daveg]

Bricks don’t insulate.

The insulating properties of firebricks are:
Thermal Conductivity 300°C : 0.2 W/m.°K
Thermal Conductivity 750°C : 0.28 W/m.°K
Thermal Conductivity 1000°C : 0.32 W/m.°K

You could place your hand on the unheated side of one that is 3” thick even if the heated side were 500°C

[wiam]

The insulating properties of firebricks are:
Thermal Conductivity 300°C : 0.2 W/m.°K
Thermal Conductivity 750°C : 0.28 W/m.°K
Thermal Conductivity 1000°C : 0.32 W/m.°K

You could place your hand on the unheated side of one that is 3” thick even if the heated side were 500°C

Sounds like someone that has not got burned on the outside of an arch with just firebricks that has been running for several hours.

[ecolbeck]

The insulating properties of firebricks are:
Thermal Conductivity 300°C : 0.2 W/m.°K
Thermal Conductivity 750°C : 0.28 W/m.°K
Thermal Conductivity 1000°C : 0.32 W/m.°K

You could place your hand on the unheated side of one that is 3” thick even if the heated side were 500°C

Its a question of relative insulating value. Any material will "insulate" you from a heat source, but nobody uses bricks to insulate their house. Typical batt insulations have thermal conductivities that are an order of magnitude lower than the ones you've reported for firebricks.

[aamyotte]

In my barrel evaporator I added 1" thick insulation on the inside sides and back. I then installed brick against the insulation to protect it. The sides of the barrel stay cool for awhile but after some extended heating the sides start to get warm after the brick has soaked in the heat of the fire. It's certainly better than without the insulation barrier.

[therealtreehugger]

And what’s better to insulate under the bricks - ceramic blanket or sand? (Provided of course you are on the flat part where the sand will not fall down)