Heat exchanger coming out of arch.

[Paperman]

Building a front pan to go with the flue pan I made last year. (http://mapletrader.com/community/showthread.php?t=10535) and need to build the arch to go with it as it is currently on a fuel oil drum arch as shown in the thread. In was planning on AUF & AOF. They may not be used all the time but want to incorporate it into the arch from the get go. Now onto the question. On the back of the arch where most use a full width transition from rectangle to round stack, would that be a good place for a heat exchanger? The plan would be build a light gauge steel box full width of the pan and say 8” wide and 18”-20” tall. This box would then have ends welded in recessed about an inch. Put in 20+/- 2” flues to let the hot flue gas out of the arch to the rectangle to round transition to the 8” stack. Now on the outside of the box mount the blowers for the firebox air to pull hot air for combustion. The fire doesn’t need to heat up the 35 deg. air as pre-heated a fair amount. Any thoughts?

[SevenCreeksSap]

I'm pretty interested in your idea but cant really picture it. The question I have is does blowing somewhat heated air do that much for the fire? Are you putting the flues inside the box? Are they to direct heat out to your blower or let the exhaust up the stack?

Im right at this point in my evap build on an oil tank and trying to figure it out for best results. If this can be added during the build and it will be better then why not.

Heres a goofy idea. Could the steam or hot air be captured somehow and forced into progressively smaller tubes to create a positive pressure that would turn a fan blade that is the blower. Once the fire was going and some steam or hot air created, it would be a self propelled blower, eliminating the electricity, which I dont happen to have yet in my woodlot where the sugarhouse is going.

[overfired half-pint]

Cold air is much denser than hot air therefor cold air contains more oxygen then hot air which will provide for a hotter fire.

[Haynes Forest Products]

You just described a steam engine. BUT for a steam engine you need pressure. NOT alot to move a simple fan but pressure just the same. The law of physics is high pressure moves to low pressure. With that in mind having steam go thru a series of tubes will increase the speed of the steam but wont increase the force of the steam without higher pressure at the source. Taking a square evaporator made out of 22 Gage steel and turning it into a steam vessel is quite the project.

Do this go get a thing of jiffy pop and follow the instructions and then envision it as your evaporator running a blower............................SORRY

[Paperman]

Cold air is much denser than hot air therefor cold air contains more oxygen then hot air which will provide for a hotter fire.

You are very correct but in this case I would not be limited by volume. If the fire needs more O2 I just open the fan damper. I am a powerhouse maintenance foreman at a papermill. We pull every BTU we can from our waste streams. With the flue gas coming out of the boilers we superheat the steam, heat the incoming air and heat the water going into the boiler. All with "waste" heat from the exhaust.

If this was an engine that can only pull in so much air I would want it cold as there is more O2 in the air to burn more fuel. But in my case the less heat I steal from the fire to get the air up to temp the more heats the pan.

[Paperman]

I'm pretty interested in your idea but cant really picture it. The question I have is does blowing somewhat heated air do that much for the fire? Are you putting the flues inside the box? Are they to direct heat out to your blower or let the exhaust up the stack?.

Yes flues are inside the box running top to bottom through the sheets closing the box. This gives you a path for hot flue gas to pass through from arch to stack. On the outside of the flues but inside the box you have an airspace that is heated by the hot flues. This box would have an intake hole and outlet for the fans. Air gets sucked into the box, heated by the flues and passed through the fan to the fire. If it was only to heat air for one fan you could blow air into the box and keep the fans cooler but with needing to feed both AUF and AOF you need to give them their own supply.



Heres a goofy idea. Could the steam or hot air be captured somehow and forced into progressively smaller tubes to create a positive pressure that would turn a fan blade that is the blower. Once the fire was going and some steam or hot air created, it would be a self propelled blower, eliminating the electricity, which I dont happen to have yet in my woodlot where the sugarhouse is going.

Yes it could be done but would need to be thought out well and would need to be on a large scale. In reality there is not alot of recoverable energy from a few PSI of steam. Now could a person with lots of time figure out a way to make a "turbo charger" out of few squirrel cage blowers from the heat and speed of flue gas in the stack, maybe. A waste of time, sure, but you would have the only turbo arch in the world:D.

[Sugarmaker]

Watching for the turbo charger details to be revealed. I can hear it cranking up now!
Chris

[Flat Lander Sugaring]

ok here goes the flatlander

on a force five theres like two sets of blowers. one looks like it blows towardas front of the arch for like AUF, the other blows to the back of arch but arch also has AOF. Now at the Maple rama the rear arch temp was around 1900F but the stack temp was around 700F, front was around 1600F.
If rear temp 1900 and stack temp 700 and the were the most efficient unit there, obviously the temp of the air didnt or doesnt make much difference and they seem to be using the heat of the arch to preheat the air going forwards.
I did here rumors that the force five was sucking so much air it prohibited the Leader arch from working properly, now that is what I heard HAhAhAHAhAhAhAHAHA ROFL LMAO.
Rumors are like ******* every one has one.

ok beat me up people:D

[Haynes Forest Products]

I thought we were talking about using the steam to turn the blower. So to say it again to restrict the steam in a square 22 guage evaporator is not going to work out well for the evap. Pumping steam into a series of smaller and smaller tubes wont increase the pressure out the end of the tube BUT it will increase the pressure inside the pressure vessal.......The evaporator.
Could you make a high pressure vessel evaporator yes could. There is a point that we cant make a completely perpetual machine out of a Maple syrup evaporator.

[SevenCreeksSap]

You just described a steam engine. BUT for a steam engine you need pressure. NOT alot to move a simple fan but pressure just the same. The law of physics is high pressure moves to low pressure. With that in mind having steam go thru a series of tubes will increase the speed of the steam but wont increase the force of the steam without higher pressure at the source. Taking a square evaporator made out of 22 Gage steel and turning it into a steam vessel is quite the project.

Do this go get a thing of jiffy pop and follow the instructions and then envision it as your evaporator running a blower............................SORRY

You mean I can make popcorn on this thing too:o

I guess my question about a self contained blower has been answered. On the flue idea, what if you built a box within a box? the inner box to let the flue gasses out ( thats what my wife claims i leave in the water closet) and th outer box to capture the heat. seems like that would also benefit by not radiating into the room as much. It seems like flue tubes might restrict flow through the evap. maybe not much if they're big enough and theres enough of them.

[Paperman]

they seem to be using the heat of the arch to preheat the air going forwards.
:D
I agree you could do it that way. My thinking was do you really want to pullheat out of the arch itself in order to pre-heat the air? Seems we put all kinds of insulation and board in the thing to keep heat in now they are pulling it out. The thought behind doing it in the stack it you are not using that heat for anything, the more you pull out after the last pan the more you are recovering.


I thought we were talking about using the steam to turn the blower. There is a point that we cant make a completely perpetual machine out of a Maple syrup evaporator.

That was mentioned but as you pointed out and I agreed to it is not practical to try and use low pressure steam to do any work. I also agree no perpetual machine. But we are adding energy with the wood. Pulling the most energy out of that wood is the goal. Now if I could talk to the guy overseas that tried to build a nuclear reactor in his garage, keep your house warm all winter adn boil in the spring, for like 10000 years on a golf ball of ore.

[Haynes Forest Products]

I'm with getting as much usable heat out of the arch and pans as possible. Its the terms that are being used. When someone sayes PULL the heat out of the arch to use the flue gases. My brain says you need slight back pressure to keep the heat in.
If you use a double wall flue pipe to capture some of the heat thats fine. Like so many fire places and gas boilers that use the same concept they expel the spent gas out the inner pipe and draw outside air in Through the outer section of the pipe.
Find a heating contractor that does alot of heatelators and ask him to save you the old style pipe it has a SS liner and a 2" airspace between the inner and outer layers.

[Paperman]

I had thought of what you are saying but dont know if I can get any sizable temp. increase with a single pipe in a pipe. Maybe but im thinking its a few hundered CFM. So many experiments so short of season. :cry:

[Haynes Forest Products]

It is a numbers game when you look at heat exchangers either air or water. I have tried every way to make a sap preheater. With jims help I think I have settled on the last heater i will use. Im glad that I dont have it built yet because I'm going to a 600 CDL RO and will need bigger tube size to feed the evap.

[len]

Preheating combustion air- page 12 diagram:
http://www.uvm.edu/~pmrc/Combustion.pdf

photo album (page 5):
http://s662.photobucket.com/albums/uu349/bkm_photos/Oil Tank Evaporator/#!cpZZ5QQtppZZ16

I couldn't locate the thread, or reference to the build- it might be within one of the AOF threads, or elsewhere???

[DrTimPerkins]

So many experiments so short of season. :cry:

I feel your pain. :lol:

[Paperman]

Ordered steel today. Need to figure what to use for flues. Thinking a real thin 1 1/2" tubing. exhaust tube is thicker than what I am really after. Time will tell. Need to see if I have enough heading tubing left from my truck.

[SevenCreeksSap]

So Paperman, did you look at that link that Len put up here. It shows the tubes running through the stack if Im looking at it right. Are you still thinking of building a box under the stack, if I read your original idea right. I'm still holding off on this part of my build while this thread runs. I can see the idea and like that it will add efficiency. Can this work with no blower at all? will the heated air flow through piping from the stack area back to the front if there is a blower setup under the grates because of suction and natural flow? It still seems to me once you got the heated air moving it would create a flow. I'm curious about this because I dont have elec. yet in the sap shack and need some ideas for efficiency and air flow. I may end up going with the car fan/blower and battery idea I saw on here somewhere until I get electricity.

[Paperman]

The above link has the general idea of what I want to do. My recovery unit is planned to be square. Roughly 2' wide 11'deep and 18' tall. The square shape is to help with a even disribution of flame over the pan. Opening in the top to allow cool air in with fans attached to the lower back to pull heated air out and into the firebox.

[SevenCreeksSap]

So it looks like the flue gasses go up the pipes (right?) that means the bottom of your box is closed off - plated off - except for the pipe openings. The smoke has to go up the pipes, which need to all direct the smoke into the 8 in round stack. Will they all be pointed at angles to the stack? :confused:
I have the same setup except I used the cut off round ends of the old tank for the "box" so its flat where it joins to the evap but arched at the top. the 8 in. stack will come out of the top of that. If spaced somewhat evenly around the botton side, it seems like they wont go up into the stack. if theyre all straight up from the evap in the center, that defeats the wide bottom with even flame across the pan.
Maybe I'll wait until you post a pic :-|

[Paperman]

The exchanger will have a cap similar to the ones you would see typically on the back of an arch, not a flat plate with a hole in it. I would take pics but have not started the construction of the unit yet. Steel is ordered and is at the warehouse but its been raining for days. Don’t want all that nice cold rolled steel to rust quickly.

[PapaSmiff]

I don't mean to get off topic here, but based on Len's photobucket - he seems to have built the most sophisticated and well-built oil tank arch I've ever seen. Flue pan, float box, steam hood, preheater in steam hood, AOF, AUF, Heated forced air, etc, etc. And a top-notch welding job on each component. WOW!:o

Len, did you forget ANYTHING?

[Paperman]

When I saw that build I was thinking I may just stop posting my stuff. Id give lefty and 1/2 of shorty to have all the equipment I can see in the back ground.:rolleyes: While there is no substitute for a skilled man, having the tools gives the ability to build his dreams. Hard to do quality work with a BFH, Clarke buzz box and a kitchen table. :D