No matter how you look at it, it is a simple thermal energy equation. Yes, the surface area will help the rate of vaporization, but it is limited to the extent of energy capable of conducting via the surface pathway. Recirculation over the same pathway will yield similar results to more surface area so long as you have adequate heat energy to back it up.
At 200k btu (58kw), that thing should rip. You have enough heat energy for over 60gph of vaporization, the problem is re-condensating that massive heat load. Tap water will be hard pressed to keep up even at optimal flow rates and ground temps. Calcification of the HE and other issues come up too.
The math is pretty straight forward as the specific heat equation you can find here
You can find the isobaric heat capacity of ethanol based upon temperature here
Once you have your mass balance you can factor by the thermal conductivity capacity of 304 or 316 (whatever you are using). That info is here
You will have a theoretical maximum vaporization rate from the above info. I say theoretical because that math assumes you are operating with no energy losses. That also needs to be factored.
Our unit is 22kw on the front end, 22kw on the back end. We hit 100lph+ (25gph+). We also added tablet remote PLC control and are going to add some sensors to optimize. Come check it out at the Vegas show. Here is a teaser link.
https://www.instagram.com/p/BpzeDvcBci7/
Hope to see you there also Dustin.