Preheater

[Super Sapper]

Has anyone tried a preheater by running their copper along the outside of the flue pan? It could be soldered along the length to get better heat transfer and should never boil out as the heat should never get higher than the boiling sap. You could run a coil on the side starting near the bottom and make a couple runs going up on each pass and then going over the top. A heat shield and insulation could be added if needed to the outside.

[Newfvt]

I have never seen one but what an idea! Why "not". Anyone who's ever stood for long against the side of a good boil in the back pan can tell ya it gets plenty hot. I think if you did put a heat shield on the outside it would retain more heat. the only down side would be whether or not this cooled the inside of the pan badly enough to effect the boil? If you use small diameter copper which is the best heat conductor, and only have flow about equal to what is going in your float box it would seem balanced. My only question is that doing this idea is going to put your "warmed sap" at or below the level of the intake side on most float boxes. That's going to mean a little circulator pump or booster in the line. Would you send this back to your holding tank or right into the float box. As with any pre heater, shut off valves, the ability to route sap around the place and by all means safety - pop off or relief valves - would be mandatory. I blew my first homemade copper preheater to smithereens 20 years ago. That is a once in a lifetime experience.

Where are you in WI? I am at Black Creek.

Steve

[RileySugarbush]

It would heat the sap fine but would be to no advantage to you since it is pulling the heat out of the sap, just as if you poured it directly in. Preheaters should take advantage of waste heat, such as in the steam above the pans or if you are daring, the waste heat in the stack. That heat is truly past the point where it is going to evaporate any sap.

As has been said elsewhere, preheating is nice and all (satisfying too!) but the best possible preheater on the coldest sap will only gain you close to 15% on efficiency or rate. More likely much less than 10%.

Use your ingenuity (and you clearly have that!) to come up with ways to get more pan area exposed to the heat and you can double the rate of flat pans easily.

[Super Sapper]

I was thinking of having the line above the level of the sap and this should not take any heat away from the sap and is wasted heat. I was looking also at regulating the flow from the head tank and the line would be full at all times to increase detention time and gain as much heat as possible. I would also have a connection on the line feeding flue or float box below the lowest level to break it apart to empty the line to prevent freezing between boils. I am new at this but it is fun to learn new things and try different ideas.

[RileySugarbush]

Ok, that wouldn't steal any heat from your sap in the pan, but I think you will find that the pan wall/ outside and above the sap level, doesn't really have a lot of heat to give you. If you move that line to above the pan, add a hood to keep it the steam around it and a tray to catch the drips and you will have the most effective and common type of preheater. You are close!