Too much vacuum?

[Mapleblood]

I've been given a double diaphragm vacuum pump that can pull a vacuum up to 29.5 inHg and pushes about 1 CFM. It only needs to work on 84 taps. I'm concerned that it might go beyond the partial pressure of water and actually boil the sap in the tubing creating a compression condesate in the pump. Any ideas how I could best use this pump?

[Spanielslovesappin]

By hooking it up to your 84 taps!

@ 29.5" Water Boils at about 55 degrees F. You will not achieve 29.5" in real world applications and almost certainly not in a maple pipeline. Even if you managed to get to 29" water will boil at 78 degrees F.

The sugar changes the numbers to your advantage and even if you were able to get your vacuum to a point where you boiled the water out of the sap as soon as the water vapor hit the atmosphere it would re-condense and return to its liquid state. Also if you started to make vapor you would have pumping losses and your vacuum would drop to the point that you were pumping sap again.

I believe that Cornell played with a vapor compression evaporator back in the day to concentrate sap; i saw it in the garage at the Uihlein forest. RO's won out as they are much simpler, cheaper and work better with less energy inputs.