soft copper tubing preheater

[berkshires]

Anyone ever tried using soft copper pipe wrapped around the flue pipe as a pre-heater? I'd have some kind of little pot or tank soldered in at the top end, then the sap would flow through the copper tubing, with a number of wraps around the flue pipe, and a valve at the bottom end. Seems like all that copper in close proximity to the hot flue pipe would heat the sap really fast.

GO

[Pibster]

I tried it a few years back. It did help a little but it probably wasn't worth the grief. Once the sap ran out each night, the remaining sap would burn so you had to run water thru the lines to clean up. I switched to a parallel flow copper preheater inside a hood, much better.

[bowhunter]

I have a 1/2 pint evaporator and an RO. I run the concentrate directly from the RO into the evaporator and I use a soft copper coil around the flue pipe as a preheater. It works pretty well. I add about 50 deg F to the concentrate before it enters the evaporator. I do rinse the preheater coil out with permeate water and blow it out when I'm done for the day.

[Bentley Wood Maple]

I tried it a few years back. It did help a little but it probably wasn't worth the grief. Once the sap ran out each night, the remaining sap would burn so you had to run water thru the lines to clean up. I switched to a parallel flow copper preheater inside a hood, much better.
I built similar pre heater 5yrs ago. Has40 ft of 3/4 inch copper inside a stream hood. Sap exiting preheater is hot (140?) but I did not see great improvement in my evaporation rate. My thought is that in a closed system you are not releasing any steam.
Have some ideas for my next pre heater but after building bigger evaporator this summer my cookie jar is empty; no more cash for the sugar house this year

[SmellsLikeSyrupNH]

This is what I am trying this year. I think having a hood will make this a more efficient idea, but right now I am not setup to add a steam hood, but I will keep tinkering.

14758

[berkshires]

This is what I am trying this year. I think having a hood will make this a more efficient idea, but right now I am not setup to add a steam hood, but I will keep tinkering.

14758

Won't any system like yours, where the cold sap is right above the trays, cause a lot of condensation to form on the pipe and drip back into the boil?

GO

[BRL]

Won't any system like yours, where the cold sap is right above the trays, cause a lot of condensation to form on the pipe and drip back into the boil?

GO

Yes it will! Smells like syrup you will want some kind of drip tray under there.

[SmellsLikeSyrupNH]

I did a test boil this weekend and absolutely saw condensation......I think this whole idea may be for naught lol. It came with my new 2x6 but it was a $hitshow of a config. I tried cleaning it up and connecting it properly and allowing it to function as designed. Even if the design is wrong. I will say for the few drops of condensation that drip in I don't think it really will effect anything. Coming out of the end into the float box it wasn't "hot", merely a bit warmer than the water temperature. The float box though, as sap is entering into that, is VERY hot. Im guessing its easily 150-160 degrees being heated by the radiant heat of the evaporator. Right now im more concerned with why this **** thing wont boil as well as my previous evaporator. Ill post that in the evaporator forum though.

[optionguru]

Do a search, a bunch of us have done a preheater this way, I did one on my previous homemade arch. One thing that helped a lot was I took the next size up of pipe and made a jacket to cover the copper pipe. In my case I think I had 6" stove pipe and put an 18" piece of 8" pipe over the copper. I was getting 120 to 140 degree sap coming out of the preheater which certainly helps but the end of the night was a hassle having to fill my preheater feed tank with water and letting it run into a separate bucket.

14778

[berkshires]

Do a search, a bunch of us have done a preheater this way, I did one on my previous homemade arch. One thing that helped a lot was I took the next size up of pipe and made a jacket to cover the copper pipe. In my case I think I had 6" stove pipe and put an 18" piece of 8" pipe over the copper. I was getting 120 to 140 degree sap coming out of the preheater which certainly helps but the end of the night was a hassle having to fill my preheater feed tank with water and letting it run into a separate bucket.

14778

Thanks for the feedback. From what I can tell from your setup, you have the tubing running around the stovepipe in a downward spiral from tank to outgoing. From the searches I've done here, it seems a number of folks found that this makes it much more likely that bubbles that form in the pipe and try to travel up (opposite to the direction of flow of the sap) wind up blocking the flow of sap. And that the solution to this problem was to run the prewarming pipe in an upward spiral around the stovepipe, with an air vent at the top (near the outgoing spout) of the prewarming pipe.

Is this a problem you ran into? And if so, how did you solve it? And if you didn't have this problem, do you have any idea why not? Did you use much wider pipe than is typical (might allow bubbles and sap to move past each other without locking up?)

Thanks!

GO

[berkshires]

but the end of the night was a hassle having to fill my preheater feed tank with water and letting it run into a separate bucket.

14778

I'm also curious about this part. What would happen if you just ran a little water through, closed the valve at the end (so the pipe is full of water), and walk away while the fire in your evaporator burns out? Would the water in the pipe boil off and leave you with a burnt pipe? So do you need to babysit it and keep the water running through it until the stove (and stovepipe) cools down?

GO

[RigaudBeach]

I just made one today for my homemade evaporator. Water comes out a little warmer, but what make it efficient for me is the fact that it never stops boiling and I can control the flow rate.16233

[Sinzibuckwud]

I run my 3/8 line into my flat pan. Two trips around the pan and I cannot touch the sap coming out. By heating with the boiling liquid I never have to worry about scorching.

[bowhunter]

That's really and excellent idea.

[Trapper2]

I run my 3/8 line into my flat pan. Two trips around the pan and I cannot touch the sap coming out. By heating with the boiling liquid I never have to worry about scorching.


Picture please?

[RileySugarbush]

I run my 3/8 line into my flat pan. Two trips around the pan and I cannot touch the sap coming out. By heating with the boiling liquid I never have to worry about scorching.

If I am understanding this correctly, you are running the tubing down through your boiling sap and back out, you are not really helping yourself much. The gain from a preheater is that the incoming sap is heated with waste heat, best from condensing water vapor over the sap pan in a hood and collecting the condensate so it doesn't drip back into the sap. Alternatively, from the waste heat in the stack, though that is touchy since the temperature can go very high and burn your sap in the tube of boil it and squirt hot sap all over someone.

If you are preheating using the boiling sap, you pay as much as you gain since the heat going into your feed sap comes from the existing sap.

[lyford]

I was thinking the same as RileySugarBush

[Sinzibuckwud]

If I am understanding this correctly, you are running the tubing down through your boiling sap and back out, you are not really helping yourself much. The gain from a preheater is that the incoming sap is heated with waste heat, best from condensing water vapor over the sap pan in a hood and collecting the condensate so it doesn't drip back into the sap. Alternatively, from the waste heat in the stack, though that is touchy since the temperature can go very high and burn your sap in the tube of boil it and squirt hot sap all over someone.

If you are preheating using the boiling sap, you pay as much as you gain since the heat going into your feed sap comes from the existing sap.
I see what your saying, and agree. Guess I never thought about it that way.
Better than dumping in cold sap, which was my alternative, this system runs itself once boiling and does save time adding cold sap slowly or losing the boil adding lots of cold sap at once. If the boil dies so does the pre heater, boil comes up sap comes out....after some fine tuning of course. Spent all my money on a woodlot so the other end is still pretty primitive, we'll get there....eventually.
I have a new stove this year and will have a stock pot over the existing top vent with direct heat more along the lines of those half pint setups, just made out of stuff around here.
Eta: Found a video on the boys phone sort of showing the setup.
https://youtu.be/zaE0feIDCKU

[Johnny Yooper]

Anyone ever tried using soft copper pipe wrapped around the flue pipe as a pre-heater? I'd have some kind of little pot or tank soldered in at the top end, then the sap would flow through the copper tubing, with a number of wraps around the flue pipe, and a valve at the bottom end. Seems like all that copper in close proximity to the hot flue pipe would heat the sap really fast.

GO I made a copper tubing preheater several years ago, wrapped tight around my chimney pipe, I pump 40f sap from an outdoor tank to the top of the tubing, spirals down and exits through a gate valve into one of my pans, checked the sap coming out of the tubing with an accurate hand held multimeter with thermocouple attachment, it read 160F; I have a gate valve on the output to adjust the delivery rate of hot sap into the pan. Prior to shutting down, I switch to water as it's a nice way to get hot water in the shack for cleaning up. I like to try something new each season simply to learn and try to make things more efficient, I might add a second copper coil to the stack this year so see if I can increase the temperature of the sap going into the pan.