Vent heat exchanger

[snoops]

Is there such a thing? I was thinking of building a air to air heat exchanger around my vent pipe, or maybe I already spent the afternoon starting to build one? Please give me one good reason to stop other than it wont work! The only thing I can think of, and maybe the reason you don't see them anywhere is because you could possible cool the pipe down too much and lose your draft? In my head it should work though I can just turn the vent blower up a little. Gonna make it out of Aluminum and put a 650cfm axial fan in it (its already ordered damn it!!). I was actually thinking of making a water to air exchanger and running a open loop system but the I thought the investment would be too much if it didn't work.
Maybe it will save me a couple bags of pellets a week, or am I just crazy. I can't leave stuff alone!!

 

[karl0525]

I have had some thought of this also. you might cool it off to much and create creosote. you will need to use single wall pipe if you want to max your heat output i thought about using a oil filter cooler that clamps onto the outside of the oil filter their hard to find and to expensive but would slide right over 3 inch pipe might be idea

 

[hoverfly]

I working on somthing like Selkirk Direct Temp. I have 10 feet of vertical Pellet pro, so I am using a 6" duct to wrap around a 4.5 foot secton. I am using two end caps cut out in the center as close to the out side diamiter of the vent pipe. A hose clamp on the vent pipe located on the bottom to hold the exchanger in place and will use high temp sealent to make it air tight. I will cut out openings to supply cold air from the top and exit the air from the bottom.

 

[snoops]

I working on somthing like Selkirk Direct Temp. I have 10 feet of vertical Pellet pro, so I am using a 6" duct to wrap around a 4.5 foot secton. I am using two end caps cut out in the center as close to the out side diamiter of the vent pipe. A hose clamp on the vent pipe located on the bottom to hold the exchanger in place and will use high temp sealent to make it air tight. I will cut out openings to supply cold air from the top and exit the air from the bottom.

Thats pretty close to what I am attempting. How are you gonna hook your blower in? Do you think you will get enough heat transfer off a smooth pipe? How many CFM is that blower your gonna use? I can't wait to see how well/if these work! Are you in the middle of this build? Very Interesting. Keep me posted.

 

[hoverfly]

I working on somthing like Selkirk Direct Temp. I have 10 feet of vertical Pellet pro, so I am using a 6" duct to wrap around a 4.5 foot secton. I am using two end caps cut out in the center as close to the out side diamiter of the vent pipe. A hose clamp on the vent pipe located on the bottom to hold the exchanger in place and will use high temp sealent to make it air tight. I will cut out openings to supply cold air from the top and exit the air from the bottom.

Thats pretty close to what I am attempting. How are you gonna hook your blower in? Do you think you will get enough heat transfer off a smooth pipe? How many CFM is that blower your gonna use? I can't wait to see how well/if these work! Are you in the middle of this build? Very Interesting. Keep me posted.

My Mini does not have a direct connection for an OAK. It just connects to the back cover, that's it. So maybe next summer I will construct a flange to plug it in and be able to use the combustion blower to pull outside air through, instead of room air. For now I’m full time student, so I have not much time to finish the project.

The plan between semesters is to connect the squeal cage blower, to the exchanger with 2" flex pipe. I might use the tangal blower, it's much quitter, and I would not need the flex hose. The blower will have a speed control and a snap disk switch (if I can find one the fits the plan) so the vent does not get to cold. Air flow will be form the top to bottom; it’s more efficient this way. As a matter of fact if I connect it to the combustion air intake, it's actually called an economizer. But for now it’s a heat exchanger for this winter.

If I use flex pipe I will make my own nipples to connect to the exchange. The other blower, when I cut out the opening I will fold it open to mount the blower, this one does not have to connect air tight to blow air through. This might be a good idea to allow heat to escape without cooking the blower.

You are not going to need a lot of air from a blower; you will need a low velocity, to pick up heat efficiently. The ones I have, the black squeal cage, is around 30 cfm. Looks like to be used in high temp application like a pellet stove combustion fan. The other one I used for a fireplace heat exchanger or room air fan for a pellet stove and this one moves up to 75 cfm. You might be able to get away with a all metal muffin fan, like ones for a pizza oven.