relationship between surface area and evaporation rate?

[brettvidler]

Hey everyone is my first post here.

My names Brett and in in hazelton BC. sorry if this is in the wrong section. feel free to relocate it if appropriate.

Ive tapped maples for a few years and now im getting into birch sap.

I am about to start making my own evaporator for birch sap and i am wondering if there is a direct relationship between surface area in the evaporator pans and the evaporated gallons per hour?


in otherwords is there an equation to figure out how much surface area i need to boil off "X" amount of sap?

Thanks in advance!!

[maple flats]

With good wood, split fine (wrist size) and dry, you can get about 1 US gal/sq ft/HR on a flat bottom pan. If you add flues (in the bottom of the pan it climbs a lot, because you have added more surface area to put heat into the sap. Look up flue pans in a search to see them. Flues cab be anywhere from a couple of inches deep up to 11-14" deep. Most common flue pans have 7 or 7.5" deep flues, older pans had 2-3 and 5" deep flues. As time went on the flues got deeper because the boil improved with the same amount of wood burned.

[berkshires]

One thing to keep in mind is that you want a much cooler fire - you just want to simmer your birch sap, or it'll burn. At least that's what I've read. So assume a much higher area needed for the same evaporation rate. Sorry, I've never done birch syrup, so I couldn't tell you the exact difference in area between birch and maple.

[brettvidler]

thanks for the tips so far. it gives a good ballbark idea for sure. im working on designing my first evaporator now. so just figuring out the specs.
Does anyone have experience with these?:
https://www.amazon.ca/Update-International-NJP-1004-Full-Size-Anti-Jam/dp/B0036C67U6/ref=sr_1_2?ie=UTF8&qid=1515432693&sr=8-2&keywords=steam+table+pan

or a better alternative?

[berkshires]

Steam tray pans are a common and easy way to get going. That's what I use.

[maple flats]

Have you tried tasting Birch Syrup? My wife and I both did and did not like it, but there are people who do like it.

[Trapper2]

With good wood, split fine (wrist size) and dry, you can get about 1 US gal/sq ft/HR on a flat bottom pan. If you add flues (in the bottom of the pan it climbs a lot, because you have added more surface area to put heat into the sap. Look up flue pans in a search to see them. Flues cab be anywhere from a couple of inches deep up to 11-14" deep. Most common flue pans have 7 or 7.5" deep flues, older pans had 2-3 and 5" deep flues. As time went on the flues got deeper because the boil improved with the same amount of wood burned.

Dave, When using a flat pan, 36 X 42 X 6 with no flues does it matter if you are boiling 1" of sap or 5"? Do you get a better boil at an inch? I generally keep mine at 3" for safety sake.

[Zucker Lager]

thanks for the tips so far. it gives a good ballbark idea for sure. im working on designing my first evaporator now. so just figuring out the specs.
Does anyone have experience with these?:
https://www.amazon.ca/Update-International-NJP-1004-Full-Size-Anti-Jam/dp/B0036C67U6/ref=sr_1_2?ie=UTF8&qid=1515432693&sr=8-2&keywords=steam+table+pan

or a better alternative?


Hey Brettvidler:
Just for your info I did a project using a steam table pan and found that the thickness of those pans are gaged by the metal thickness "BEFORE" stamping into a pan so the edge is maybe 18 GA. But if you drill a hole through the bottom of the pan where it was thinned out by stamping it will be half that or less. Might not be a problem for you but just thought I'd let you know. Jay

[Haynes Forest Products]

There is also a relationship between the amount of flues, there size and the how deep you run the liquid. Then you factor in to surface area of the pan itself. Plus the temperature of the surface and any restrictions the hood might create. Taking into consideration any underside flue insulation created buy soot build up. Once you can determine the speed the combustible gasses pass over the flues along with the friction created by the turbulence from carbon deposits. There is a very close relationship between the draft door and your flue stack compression ratio that develops when your flue stack has wind flowing over it. I have found that having a square flue stack will offset the effects of wind direction and lesson the need to keep moving you sugar shack around to be in Feng shui with the Aurora borealis will help stop internal fluctuations of the turbulence during fuel insertion. Once you learn to compensate for these changes on your Barometer you will be more efficient. I remember back in 89 we had these same conditions and with a few changes we were able to over come there effects.

[Haynes Forest Products]

Please forgive me I an suffering from the effects from eating 6 sleeves of frozen Thin Mints and 2 beers on a empty stomach. :(

[Mikemartin274]

n old timer once told me you get about one gph for ever y one square foot of surface area.

[Haynes Forest Products]

I get about 5 times that on my 3X10

[berkshires]

I get about 5 times that on my 3X10

I'm guessing it's not a flat pan. LOL.

Do the math on the surface area of all your flues. I bet you don't really get five gallons per hour per square foot of surface area.

GO