Thoughts on another preheater

[DoubleBrookMaple]

I haven't really tested my boil rate of my 2x4 Smoky Lake hybrid pan, but thought a preheater wouldn't hurt. I have my homemade arch with a base stack I welded up from angle and sheet.
Last year I wrapped copper tubing around the stack on my block arch.
Here is what I cam up with. 1/2" copper tubing, with an outlet temperature probe to keep the temperature from boil. I can adjust the distance from the stack, insulate or shield the pipes to keep heat in, or away depending on how much heat transfer I get. The top will swivel out, away from the stack heat if need be. I have no idea how it will work yet. My test boil the other day before I did this, my stack temp was 1000-1200, and with 18ga sheet it should be quite hot, I have plumbing to run off my head tank direct to float box, or through the preheater. This way I can isolate it if need be.
I have an ongoing thread on the arch here...
http://mapletrader.com/community/showthread.php?21969-New-2X4-arch-build-for-Smokey-Lake-Hybrid-pan

Here is what I am toying with now...

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[chad]

we had a preheater madde the same way, the problem with it was when the float box wasn't open the sap would burn in the tube

[TerryEspo]

It looks great. I hope it works as planned. I am toying with a new type of preheater also, I didn,t like the copper tube wrapped around the pipe, burnt sap at times, too hard to remove tubing once there was no more sap etc.

For us small guys I feel a removable preheater is best, just not sure what that is yet, lol.

Good luck to all.

[DoubleBrookMaple]

Thanks for the thoughts..

I have made it so it will swivel out away from the heat at the top away from the heat to control the temperature. Another thought is to have an insulative barrier that I can slide between, that can function as a variable temperature control system. I can monitor the outlet temperature and make the adjustments as required. In addition, I have a bypass system, and can drain the tube, but that needs another valve at the top to open to atmosphere. I can open the float valve manually, and the tube will drain.
I have about 60-70 gallons of sap from the past week, and will try it out today, for my first real boil test. I boiled with water a few days ago before I added this preheater.
Operationally, I think the way to go is to bypass the heater with the heat barrier in place until boiling, and a constant flow of sap is established. Then open the heater valves, establish a flow thru the tubes, then remove the barrier, monitor the outlet temperature to slowly raise the temperature to the desired level. Once a steady-state boil is established it should be easy to just monitor and control. Like you folks said, and I learned myself last year, vaporizing is a problem with high temperatures. Last year even with my crude preheater, once a steady-state was established, I could run it for hours with an outlet temperature about 100 deg. from initial sap temperures in the 30's. I would like to get more from this one.

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My preheater last year...

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[TerryEspo]

Hey Eric:

That fact that your new preheater swivels is great. Fantastic idea. Sounds like a keeper to me.
Your system last year was the same as mine, lol. That is why I am changing also.

Looking forward to hearing how your boil goes today.

Thanks.

[DoubleBrookMaple]

Tested preheater installation with sap today, and found the preheater is not adequate. I only got a 20 degreee rise in sap temp, and that was after wrapping/enclosing with blanket to retain heat. I also had added a vapor relief tube at inlet to preheater vented to atmosphere above head tank level. This was added to eliminate and vapor lock type problems from any boiling that may occur in the preheater tube.
I will need to modify or redesign completely. Maybe some sort of heat sink, or aluminum fins to capture and transfer for heat from stack. Maybe build an enclosure as well.

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[sapdog]

Sorry to hear the first run didn't go as well as hoped, but this setup looks promising. Looking forward to seeing the next steps.

[lpakiz]

How about an aluminum-finned, copper-pipe type of hot water baseboard heater?

[BreezyHill]

I cant take the credit for this design as it was my dads from 20 years ago.

Hood made out of the old aluminum plates that the newspaper used to print the paper. From here the steam is plumbed in a square duct to a 3/8" plywood box about 8' long.

The steam enters at the bottom right of the box and travels to the left in the lower half of the box. Upon getting to the left end it travels up to the top half of the box and back to the right to exit thru a 6" duct up and out of the building.
A stainless pipe of 1.5" takes the sap thru the bottom half of the box and thru the duct that brings the steam from the hood. The steam duct exits the hood over the float box inlet where the sap tube exits the steam bath and into the float box.

The box is tipped so as to drain all condensate to a drain. Sap temp in system last weekend was 33 degrees and 183 at the float box.

This is on a 2x6 air tight that averages in the mid 40's per gallon this season on two boils so far.

Dads design had a double 1.5" copper that started leaking the last boil of last season. Copper has a better heat exchange rate but corrodes more than SS.
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[DoubleBrookMaple]

I cant take the credit for this design as it was my dads from 20 years ago.

Sap temp in system last weekend was 33 degrees and 183 at the float box.

Very Nice! That is more like what I want with just 25 gph or so. I will come up with something.

[DoubleBrookMaple]

How about an aluminum-finned, copper-pipe type of hot water baseboard heater?

I was trying to think of how to attach fins, but maybe I should consider buying a baseboard heater. They are just $15 ea for two footers, but, come to think of it, I could get a long one, and cut it up and re-plumb it to make a heat exchanger to fit my stack.

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[CampHamp]

Eric - quite an ingenious setup! Even though the blanket looks like it should work, you're going to create ceramic dust moving that around. I like your swivel idea best. Please be cautious, esp. with kids around.

[DoubleBrookMaple]

Eric - quite an ingenious setup! Even though the blanket looks like it should work, you're going to create ceramic dust moving that around. I like your swivel idea best. Please be cautious, esp. with kids around.

Yea... I was just using it temporary for testing purposes. If I did use it, I would have encapsulated it in something. I will set up a good swivel system with my new design using slant/fin heater pipes.

[DoubleBrookMaple]

Ready for test...
I just hope there is enough heat radiated from the stack to do anything.

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[Ausable]

Eric - I like the way your brain works. Looks good to me. Any heat going up the stack is wasted - It can't be helped - but it is wasted and not efficient. You are coming up with ideas to harness some of this wasted heat and using it. Remember - If You market any of Your ideas make them shiny-stainless as that is what the big producers like. Keep up the good work and best of luck.

[TerryEspo]

Very nice Eric.

Love the idea of using heat from the smoke stack, once in the stack its gone,,,,until Eric, lol...no longer wasted heat.

Great job !

[Michael Greer]

So put a thermometer in it and let us know what happens. Every little bit helps.

[D a v e]

I don't believe you want the fins on your piping they are to distribute the heat from pipe not pull the heat in to the pipe they are acting like cooling fins on the head of a motor if you run straight copper tubing with out the fins it should run hotter.

[DoubleBrookMaple]

I don't believe you want the fins on your piping they are to distribute the heat from pipe not pull the heat in to the pipe they are acting like cooling fins on the head of a motor if you run straight copper tubing with out the fins it should run hotter.

I believe you are right, to an extent. We will see. Just as radiators cool the water in your engine by passing lower temperature air across the fins, I believe the hotter temperature air will heat the fins, and in turn heat the sap. Not efficient maybe, but it will work on some level. The hot water coming out of the baseboard heater is cooled by the lower atmospheric air in a house. I believe the sap coming out of my unit will be heated by the higher temperature air in my preheater chamber.
It has to do with heat transfer. I first thought of submerging copper pipe in hot water, as water is such a good heat conductor. The aluminum fins will transfer heat to the copper pipe, and therefore into the sap.
Once again, if you are radiating heat from a baseboard heater, you are cooling the liquid in the pipe. Why will it not work in reverse?
Anyway...
I have no doubt that fins are normally used for cooling, and not heating. Now I want to go out and test it.

We need a physicist to chime in.

[Big_Eddy]

Are those heater cores lead free and food safe?

The fins will transfer heat from hot to cold so will work "in reverse" as you hope if you can keep the air hot on all sides. You will be best served if you can contain the entire thing within an air chamber surrounding the stove pipe. Don't forget your vent in case it does boil in the tubes.

Next you will want a thermocouple in the exit stream attached to a damper door motor to open and close it based on the exit temperature. 210 open. 180 close.

[DoubleBrookMaple]

Are those heater cores lead free and food safe?

Don't forget your vent in case it does boil in the tubes.



HaHa!
I actually did forget the vapor vent. I had one on the original, and didn't remember until afterward, so I have to break into the line with a tee.

[DoubleBrookMaple]

Finally got to test the latest preheater today.

Not a real success. Sap temp was 40, and outlet was running 80-90 degrees. I will live with that this year, and improve somehow for next year. Sap is finally coming in, and I have to keep up with it now. Started with about 230 gallons today from yesterday, and overnight, as it only got down to 33.
I boiled for 7 hours total at 20 gph.
**UPDATE** Preheater today ran 90-120 all day.
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[KevinS]

what is the total length that does the heating?

[twin6]

Are those heater cores lead free and food safe?

Yes. I've used BB HW heating elements for a preheater for two seasons, taking advantage of heat loss above the pan next to the stack. The pipe has nothing soldered inside. The fins are pressed onto the outside.

Eric, congrats on a nice job. Have enjoyed your threads and watching the progress.