Increase Pan Efficiency?

[MapleMark753]

Hello-- I have been trying different ideas to increase efficiency in boiling, and a different thread here piqued my interest in pan efficiency. I am not a maple expert by any means, (this is just our third year) but in my past career I was trained in and became fairly good at elements of heat transfer, what it does, and doesn't do. So, back to pan efficiency. I had thought that some type of coating on the bottom of pans (flat for now in my instance) may increase boiling efficiency. Most use stainless steel of some sort, and a lot are polished. This is good in many ways, but may not be the best for heat transfer to the sap, which is what I want. Polished stainless will reflect quite a bit of the heat exerted on it. That part of stainless isn't optimal. I got some 2000 degree paint, painted (several coats) one half of the bottom of a stainless pan and left the other half plain stainless. The color is flat black. Flat black is probably the best color to use, I think. I put the pan, with two inches of water in it, on a double propane burner, and watched to see what would happen. Long story short, the heat painted side boiled, the unpainted stainless did not boil at all. I used a medium heat level. The unpainted side would have boiled, but I shut it off after seeing the painted side boil vigorously first. Then after shutting it down, I waited a couple minutes, and tried to grab the pan by the ends to lift it off the burners. Mistake, but there was good info there, as the painted bottom side was still too hot to handle, while the unpainted side I could hold on to. Lastly, I looked at the bottom of the pan afterward, and the heat painted side had no burning, no bubbling of the paint, and appeared fine. I can post pics, if anyone is interested.
I don't think anyone would try this on expensive new pans, but I believe that its repeatable by anyone, if someone could try it. Not saying this is an original idea, and others may have already done this, or discarded it for all I know. BUT, it looks promising for an incremental increase in boiling efficiency. I'd be interested in anyones thoughts on this topic.
take care, Mark

[Amber Gold]

In a wood fired arch, the bottom of the pan soots up black anyways, so nothing would be gained...IMO.

[MapleMark753]

Well, you're right of course, they do soot up pretty good on wood fired. I won't find that out personally until next year when switching from propane to the Lapierre I've ordered from Chris. The pans soot up a bit too on propane, if you have the burners to where there is incomplete combustion. I get that sometimes. Soot in general though, I believe, because its a loose form of carbon, acts in maple boiling more as an insulator than a absorber/re-emitter/transferrer of heat. I think its accumulation would decrease efficiency in any type of boiling, not help it. I see from your posted "bio" that you're much more experienced in maple syrup than I am, but we're expanding and getting there. Thanks for your thought. Mark

[red maples]

yes I was gonna say the same as josh did. With wood especially you will get a layer of carbon on there after the first fire. even if its a few minutes. the trick is to controll the level carbon as the season wears on and the carbon builds you will loose heat transfer to the sap in the pans. I brush them before each boil to help with the problem. there has been many new inovations in arch development such as forced air, air turbulance and where the force air is place under fire, over fire or forcing it back and mixing the air to get a more complete burn of the gasses given off by the wood or other products. this equals less polution and a hotter longer burn of the fuel being used (mostly with wood) The pans are pretty much what they are. Copper is an excellent conducter of heat but its getting as expesive as gold these days. I would say a copper bottom coated stainless pan would be your best choice but I wouldn't want to see the price tag on that one!!!

[bowhunter]

The pans are going to soot up because the temperature of the pan is so cold relative to the wood flame and you're getting condensation of incomplete combustion products. You're right about the heat transfer. More than half of the heat transfer is radiant from the flame and the best receptor is a perfect black body so painting the pan black for propane probably did increase the heat transfer. I think the amount of soot on the bottom of the pan in a wood fired evaporator probably reaches an equilibrium were if the layer gets too thick it gets hotter and burns off. I think if you measured the thickness of the soot layer 3 hours after the first boil it would still be about the same at the end of the season.

[Amber Gold]

I generally don't clean my pans during the season (usually forget), and don't find the soot any worse than when I do. I agree with bowhunter, it must burn off or something.

[maple flats]

What would keep the flat black paint from sooting up? Once sooted up you have the same issue as with bright SS that is covered with soot.

[MapleMark753]

Hello- I don’t know the answer to the questions regarding soot on the pans in a wood fired evaporator negating the effect of a coated pan coming to a boil faster, and boiling faster, so I did another experiment today. It will have to be the last one this season because although I definitely have the Maple Bug, other things like work and family place certain limitations that aren’t necessarily bad!
Anyway, what I did today is I took two SS pans of equal size, coated one pan bottom with flat black high temp paint (several coats), filled each with one gallon of water, and put them on an open fire (on a grate) to boil and see what happens. The coated SS pan came to a boil in 5 minutes. The non-coated pan came to a boil in 8 minutes. The coated SS pan took one hour and five minutes to boil dry, the non-coated SS pan took one hour and fifteen minutes to boil dry. That was round one. Round two was to make certain both pans had a good deal of soot on them (they did), refill them each with another gallon of water, and put them back on the fire to see what happens. The coated pan again came to a boil faster than the non-coated pan, and the coated pan boiled dry in one hour twenty minutes, the non-coated pan boiled dry in hour fifty one minutes. ( the fire was lower the second time is why they both took longer to boil dry) That’s my data on this, and I don’t know for certain exactly why the sooted and coated pan came to a boil faster and boiled dry much faster. I believe it has to do with the coating being very smooth, being hotter, and having an emissivity rating close to one. I don’t have the deep pockets or time to figure exactly why it happened this way, but at least THIS experiment gave information that suggests a pan bottom coating of flat black high temp paint would have measureable improvement over a non coated SS pan. Nor, do I know any long term effect on either the coating (durable?) or the Pan set. I would say its worth investigating further because at least to me it seems to say less boiling time, less fuel, and less work. I know I would not suggest to coat any expensive pans now without further investigation, but I may coat ( and properly time cure) a few flat bottom ones to use for finishing over propane if I need to. Thanks for your comments, take care, Mark

[Shawn]

We to get the build up of soot but this year for some reason it was not as bad. This year we insulated the arch and had a faster and all the time boil, I try to take the front pan off after two days of boiling and clean it and found the bottom not a big problem as years past. Used SOS pads and then power washed and came out sweet. At the end of the year did the same again with front and back pans and worked well. Luck I guess. Our force air fan is also in front.:cool:

[MapleMark753]

Well, I gotta say, that's the last time I put time and effort into a forum here! Bowhunter, Maple Flats, thank you for your comments on the pan bottom coating subject.
It worked over propane, and worked over wood fired too, even with soot. Its easily repeatable if you were to try it. take care, Mark

[RileySugarbush]

Well, I gotta say, that's the last time I put time and effort into a forum here! Bowhunter, Maple Flats, thank you for your comments on the pan bottom coating subject.
It worked over propane, and worked over wood fired too, even with soot. Its easily repeatable if you were to try it. take care, Mark

MM....Don't dispair! I found your premise interesting and insightful, and your experiment useful. I think it is worth further work on syrup pans, which are exposed to direct radiant heat of the wood fire. I wonder if it is as useful on flue pan where the primary heat transfer is convection? I may try and repeat your experiment with my syrup pan and water in a couple of weeks, after I am rested up from a long season.

Thanks!

[500592]

I don't think they were trying to be rude or anything you were the one who came on here and asked everyones opinions so I for one thought that is was a pretty interesting experiment but I also THINK that there would not be a benefit to doing to wood fired pans...IMO

[MapleMark753]

Yeah, you're right, I did ask for opinions. Thanks for your comments. I'd still like to see a handful of people try a pan bottom coating and see their results as compared to mine. If it turns out to be a fluke, or bunk, I say discard it. If it turns out good, people could use it for very little cost and see a marked improvement in boiling. For comparison purposes, if anyone else were wanting to try it, I used a high heat resistant, 2000 degree, flat black, spray paint after cleaning a SS pan bottom. I used several coats. I didn't cured it in the oven first (its recommended to do so) It cost around 7 bucks. And again, it worked in my brief experiments with propane and open wood fire, with soot and without soot. take care, and good luck all. Mark

[maple flats]

Well, I gotta say, that's the last time I put time and effort into a forum here! Bowhunter, Maple Flats, thank you for your comments on the pan bottom coating subject.
It worked over propane, and worked over wood fired too, even with soot. Its easily repeatable if you were to try it. take care, Mark
Mark, please keep trying to come up with new ideas, that is one of our best attributes. I did not intend to insult you. You asked for opinions, I gave mine. There is an old saying about opinions, they are like @$$holes, everybody has one and most stink.
On this forum we hash over all sorts of new ideas and that is how we expand our learning.
If your black paint idea does have lasting merit, I question how well paint will hold up with an intense fire against it all season. The next approach might be a black factory finish (annodized or something?).
When you ask for opinions (and even when you don't) be prepared to get them. Sorry if I insulted you.
Dave

[MapleMark753]

Thanks for the encouragement, appreciate it! I wasn't insulted, just pumped, and didn't see beyond my small focus at the moment. My bad. If anyone is within driving distance from me, I do have firewood, pans, paint, etc., and I would re-arrange work here to do another look see test fire and boil over an open fire. On to other work for now, and looking forward to late fall (test taps) and next regular season. take care, Mark

[lpakiz]

how well paint will hold up with an intense fire against it all season
Dave, because the pan bottom is liquid cooled by sap/syrup, would the paint get all that hot?
I too find this experiment intriguing and will follow this thread. Sometimes the simplest things have been overlooked for ages.

[RileySugarbush]

how well paint will hold up with an intense fire against it all season
Dave, because the pan bottom is liquid cooled by sap/syrup, would the paint get all that hot?
I too find this experiment intriguing and will follow this thread. Sometimes the simplest things have been overlooked for ages.

Your point would argue for the thinnest coat possible that gives a nearly complete black coating. That is what I will try.

[b116757]

Just finished a 2'x4' propane fired finishing pan may very well try the high temp paint don'tthinkit can hurt

[MapleMark753]

Good luck with your tests, those who give it a try. If it works and is durable, great! If not durable, there should probably be a list of alternative material(s) to try. I'll test just about anything, depending on the cost.
There is another side to the equation though, in addition to any pan bottom coating that may work. It also is directly exposed to the fire side of the arch. It would have to be a thin,thermally reflective material that would lay in the arch, be angled toward the pan bottoms, and reflect thermal radiation from the arch to the pan bottom. I'm talking about a material for over the insulation, all inside the arch, that would retain a lot of its thermal reflectivity even soot covered. I don't think stainless would do it (soot), but don't have any other ideas. If someone had an idea for THAT material, I'd try it too. The only other thing I can think of that would work is Cornings Gorilla Glass, its actually synthetic amythist I think, and would be cost prohibitive anyway.(its what is used on most of your smart phone screens) Anyways, the two paired (pan bottom coating, thermally reflective arch lining) could make a significant increase in efficiency. take care, Mark

[Diesel Pro]

I have found the best way to increase the efficiency of the evaporator is by using RO. ;) I'll seriously look into the BBQ black paint on the underside of my pan though too.

This season I started with literally 0 dry wood. I used a bit over 1 face of punky elm from a standing dead tree plus a bit over 1/4 face of dry oak. Once I got the RO running to the 12-14% range and the dry oak the wood consumption dropped dramatically. For next season I have plenty of oak logs to be split and I have a 4 way wedge on my splitter so I plan to split it down small to baseball bat or smaller chunks. I also have quite a bit of poplar to get rid of as well as maple so I'll probably mix this in as well.

[MapleMark753]

I can't argue with you on the RO front, I think that is a wonderful thing to use. I spoke with Steve Childs the other day about that subject, he gave some good leads which basicly supported the direction that others here have already taken in regards to membranes, pumps, motors, etc...and helped me narrow down choices for our own use here at our place.
In regards to the pan bottom coating, one thing I didn't mention is that while boiling on the fire the coated pan boiled more evenly throughout the pan than the non coated one did. The coating probably spread the heat around more evenly than just the bare fire did. And, the coating I used for the pan bottom was 2000 degree rated I believe. (there are many lower rated coatings, ie., 500, 1000, 1200, etc...)
Lastly I saw that fireplace reflectors online used anywhere from 14 to 18 or higher gauge SS. Inside an arch, on vertical or angled surfaces it may be something I will look into to reflect heat from the fire side of the arch to the pan bottom. One thing I know is that there is an awful lot of wasted heat just going up the smokestack, and that more probably can be used to actually heat and cook the sap.

[Algonquin]

Hi all, I was wondering ,how would a ceramic coating work, like on tuned headers of exhaust systems. There it's used to contain heat . I have no idea how it would work to transfer heat. Would one of you guys with a engineering back ground comment on this. Thanks Tom
I'm a half pint guy this year, 35 buckets .
Last year 10 buckets, pots and turkey fryers(2). 2 1/2 gals. Syrup last spring.

[MapleMark753]

I haven't tried it, but there is a company called Ceracote I believe, that has this stuff you can buy. They have different prices, and sizes, for example, a pint is 60 bucks. If its durable it might work, below is a bit of data on it just copied from a website. I found interesting that it looks like it has a pretty high emissivity rating.
Here's the data:
Cerakote Glacier Black Ceramic Coating Technical DataCerakote's new C-7600 Glacier Black not only looks incredible with its rich, deep satin black finish, but has the technical specifications to make it the industry leader in ultra high temperature ceramic coatings.
For more technical specifications, download the entire C-7600 Glacier Black Tech Data Sheet here.
Adhesion (ASTM D3359) - 5B (Rated Excellent in Hot Adhesion)
Pencil & Scratch Hardness (ASTM D3363) - Pencil: 7h / Scratch: 6h
Impact (ASTM 2794) - 72/20 inch-lbs.
Mandrel Bend (ASTM D522) - 2mm @ 180˚ Rotation
Salt Spray (ASTM B117) - 1051 Hours
Thermal Conductivity (ASTM E1461) - 0.03 W/m-K
Thermal Diffusivity (ASTM E1461) - 0.2 mm2/s
Specific Heat (ASTM E1461) - <1 J/g-K
Emissivity @ 70˚F (ASTM E408) - 0.92
Emissivity @ 1200˚F (ASTM E408) - 0.91
take care, Mark

[HyeOnMaple]

I'm surprised no one has recommended dropped or even raised tubes as an alteration to Mark's flat bottom pan. I had mixed results last year but that's because I crowded the tubes. I wound up having a solid wall of soot at the front of my altered pan, very disconcerting but fixable. I hacked half of them down to size and have great hopes for next season. If I were to do again, I would space them at about 3 inches apart.