[Richard L]

Put this scenario to the extreme, it you are able to spray a single molecule of water, there are no cooling effect at all. The heat absorption capacity is defined by the breaking up of the molecules held together by the van de waal force.

As far as I know, the rate of evaporation is directly proportional to the surface area solely. A droplet of water at 10 microns may have a few thousands molecules stuck together. A droplet at 100 micron be bigger and more molecules but the surface area exposed of each molecule exposed to the heat source is actually smaller. This is where the expression of enthalpy becomes useful. A total energy of a thermodynamic system.

I don't quite understand your comment about 15psi and 1000psi, please explain.