fan blowing on evaporator pan

[sirsloop]

I see all sorts of things people do to make their arches more efficient, but I haven't seen anyone put a fan blowing steam away from their pan. Water evaporates faster when a fan is blowing on it...less humidity in the air at the water to air interface. I'm not sure why we don't see people rig up fans, especially outside! Any input? :confused::confused:

[DaveB]

I had that idea a few years ago and then someone pointed out that you would actually be blowing cooler air over the surface and thus reduce evaporation. I never tried it because it made sense to me - it's kind of like blowing over a hot bowl of soup. You wind up cooling it.

[mellondome]

Yes, you will omly cool the surface. This is why you will get a slight increased boil rate if you use a hood... no cold air gets to the surface.

[Bucket Head]

Take it from someone who boiled outside for years- you don't want anymore air blowing across your pan than what Mother Nature is already blowing at it!

Very, very hard to maintain a boil and get accurate temperature or hydrometer readings.

The hotter the better when boiling. Hang onto the fan for when your bottling up some syrup in the summer, lol.

Steve

[sirsloop]

that makes sense... when I'm brewing beer in the warmer months I rig up a fan to increase evaporation... didn't think about the cold offsetting the gains this time of year, especially with all the new sap you're adding in constantly

[brikel]

As I read the posts on this thread I was wondering if an exhaust fan above the pan is detrimental to boiling rates. I have a new rig this year I did a test boil this past weekend and had so much steam I couldn't see. ended up cutting a hole in the ceiling which I will finish like a cupola. I was wondering if I could vent it some way?

[mellondome]

As I read the posts on this thread I was wondering if an exhaust fan above the pan is detrimental to boiling rates. I have a new rig this year I did a test boil this past weekend and had so much steam I couldn't see. ended up cutting a hole in the ceiling which I will finish like a cupola. I was wondering if I could vent it some way?

Put a hood on the pan and run the pipe out fhe roof.

[Helicopter Seeds]

Interesting question - The increase cooling at the surface is also a product of the evaporation. Just like the energy behind a hurricane - comes from the latent heat of evaporation of the ocean. Blowing on a boil definitely settles the foam and violence back, but I would not be so sure that it is slowing the evaporation rate. But as Werner Von Braun said, "one test is worth a thousand expert opinions". So I am convinced that someone shoud try it on a small scale, where the btu input can be controlled.
On the same token, an arrangement could be made similar to distillation process, where a vaccuum could be set to the evaporator. Recall you can get water to boil at room temp if you lower the pressure. Even a moderate vaccum should lower the heat required to boil, and thus probably lower the total time, since you don't have to heat as high. You would need a water level gage of sorts to know when you are done. Seems many of the veterans here have vaccum pumps for sap collection, that is another experiment I would like to hear about. For me, I am still too new and just getting going beyond a backyard pot.

[DaveB]

Interesting question - The increase cooling at the surface is also a product of the evaporation. Just like the energy behind a hurricane - comes from the latent heat of evaporation of the ocean. Blowing on a boil definitely settles the foam and violence back, but I would not be so sure that it is slowing the evaporation rate. But as Werner Von Braun said, "one test is worth a thousand expert opinions". So I am convinced that someone shoud try it on a small scale, where the btu input can be controlled.
On the same token, an arrangement could be made similar to distillation process, where a vaccuum could be set to the evaporator. Recall you can get water to boil at room temp if you lower the pressure. Even a moderate vaccum should lower the heat required to boil, and thus probably lower the total time, since you don't have to heat as high. You would need a water level gage of sorts to know when you are done. Seems many of the veterans here have vaccum pumps for sap collection, that is another experiment I would like to hear about. For me, I am still too new and just getting going beyond a backyard pot.

I think anyone that boils outdoors can attest to getting a better evaporation rate when there is no wind or air moving over the surface. I know from the years that I did boil outdoors that I got a much better rate when I covered the pan and didn't allow even the slightest breeze (like from a pan) to affect it. Everything else stayed the same so it was just air moving over the surface that affected it.

In terms of boiling in a vacuum, check out this thread:

http://mapletrader.com/community/showthread.php?22057-evaporating-sap-in-a-vacuum

[killingworthmaple]

I talked to a scientist about this question last summer and they claim if you can remove the water laded steam and replace it with dryer air you will evaporate faster. I personally have plenty of heat under my pans sometimes more than I need and have to dial down the fire. Also I have found that I get more evaporation on a dry day than a humid one. But the proof is in the testing we will see.

Nathan

[sirsloop]

well it makes sense that if you have a fan blowing on it it'll evap faster... really the problem would be how much heat you can get into the pan. There is a point where the amount of heat you have makes a fan add to the evap rate. If you can just barely keep a boil cause you have lots of heat loss out the sides then it wont help.

[mellondome]

Mine always had a fan blowing on it and it increased the boil rate....

just it was blowing from the bottom side ;-)


Now if you could blow 800*f exhause air over your pan, i think it would work. But I think you will find that the air in your sugarhouse is not very dry.. relative humidity speaking. Which to create dry air will now require heat.

[Cedar Eater]

Mine always had a fan blowing on it and it increased the boil rate....

just it was blowing from the bottom side ;-)


Now if you could blow 800*f exhause air over your pan, i think it would work. But I think you will find that the air in your sugarhouse is not very dry.. relative humidity speaking. Which to create dry air will now require heat.

You could take outside air and heat it with an exchanger on your stack, but if you draw the stack gas temperature down below condensing, you get soot problems.