What do you think of a 3 vessel system mash/kettle tun + lauter tun + whirlpool tun?
it is easy to use a step infusion mashing method because the mash/kettle vessel is able to assemble an agitator inside the tank. The whole three vessels only have one with heating function.
Lauter is a special unique function for lautering only. Whirlpool is another special unique function tank. I guess it is really a germany style design.
Germany brewery system also treat the lautering and whirlpool as special function and the tanks are with exactly H/D which is a little fat than mash/kettle tun.
Now i think it is also popular to make a fatter lauter tun in most of the breweries because the craft beer always in high OG. A normal standard design for lauter tun will
generate a very thick grain bed, thus low efficiency of grain usage and hard filtering. Whirlpool, i think will also come to important which the tank bottom will be in various style. Cone has been out.
In this configuration, the mash/kettle vessel can be steam heated or directly fire heating.
I do agree with riprap that the efficency is not its advantage. Only after the first batch brew is in whirpooling, you can start the second brew, unless do second mash in lauter tun.
Many breweries use mash tun + lauter tun + kettle/whirlpool vessel to do double brew in a day. It is also a classic conbination. For myself, i like this one more. However, it is not perfect.
The agitator in kettle will affect the whirlpool more or less. Or never put an agitator inside the tank. This system will request two heated tanks.
It is also possible to do mash in kettle/whirlpool vessel or do boiling in mash tun. The system will be mash/kettle/whirlpool(design specially) + lauter tun + kettle/whirlpool/mash vessel.
Does it make sense?
If you have enough space and budget, four vessels is the perfect and each tank has its own task. Never do spare time job.