I make my own Maple syrup and have to boil away lots water from the sap to make syrup. I have a propane burner and a wide roasting pan and a deep stew pot, both hold about the same amount of sap.
My question is does the wide pan make the water boil away quicker?
Intuitively, it feels like the more surface from the pan would allow more steam to escape.
However, it seems that the wider pan with more surface area would have more heat transferred to ambient instead of into the sap
[Physics] Does water boil faster in a shallow wide pan or a deep pot
evaporationthermodynamics
Best Answer
Here is an intuitive way to think about it:
A puddle on the ground will evaporate even if the water is not boiling. The same amount of liquid would take much longer to disappear if it were contained in a cup.
There is a nice microscopic reason for this. Imagine each water molecule in the center of the liquid as being "boxed in" by 26 neighbouring molecules (as if it were in the center of a 3x3 rubrik's cube). All these neighbours attract the central one and lock it in place. A molecule on the surface will have 9 empty sites above it. If it gets knocked around by its neighbours, sooner or later it will be kicked into one of the empty sites and evaporate.
You want to maximize the number of water molecules exposed to empty sites. With a sufficiently wide pan (imagine one that is so big that the sap is only 1 water molecule deep) you could evaporate the water almost instantly even without external heating. The external heating will only give the flat pan a further advantage.