Higher efficiency propane evaporator?

Hey all,
I haven't noticed a thread on this but am considering it as a project before the sap runs... a friend of mine borrows my propane cooker to boil off sap to try to make syrup. I am leading him down the path of trying to do it right but never see him going in whole hog. This year I wanted to help him be more efficient than the single big pot on the fryer so I offered him a restaurant pan to have greater surface area. The thing that bothers me is that there is still so much heat that is wasted and never transferred to the sap. So I have started contemplating building a "Davy Jones" style evaporator with leftover arch board to insulate, a full and a half size restaurant pans(from my barrel stove days), with a single 55k BTU burner for the only heat source.

My question and concerns are about whether it will generate enough heat to get good boils, or will it just be a slow simmering dud. I figure if I can get inside the box temperatures of 600-750F I should be able to get good boilage. I know that flames will not tickle the bottom's of both pans, but does it have to when the temperatures are this high?

Any thoughts, experiences or considerations would be greatly appreciated before I embark on this endeavor.
Thanks,
Chris

Chris,

Check out Micro Maplers thread in bucket/brix section. Look at Rangdales posts #51 and #53. The only consideration that I have experienced with propane is the intense heat melting the rubber tubing (3 turkey fryer's inside a block arch). Keep safety in mind as well too.

SDdave

I use propane now. I like the convenience of starting and stopping when I want. I started with a similar rig, turkey fryer burner on old sink. Worked ok if you didn't put too much sap in at a time but, as mentioned, you loose s ton of heat around it. So I thought I would be smart and built an enclosure around burner. Burner would not work properly until I made more airspace around floor to let fresh air in. Last year a bough this from lappierre..

Attachment 9228

It has 3 burners that cover entire bottom of evaporator. It works great but same thing, you loose alot of heat. Tried closing it in more and burners wouldn't burn properly. So most likely you will only be able to obtain boil where burners are and make sure you allow enough space for fresh air in and exhaust out.

my only experience is what I am going through now. I put a 300,000 BTU natural gas burner to replace the fuel oil burner I was running in the arch under my 2'x4' drop flue pan. No where near enough heat to run efficiently
yes I know it is natural gas and not propane....