How would one go about sizing a system like this?
Say you want it to service two fermenters, each with an effective jacketed heat transfer area of 0.4 m^2, and you have a 5000 BTU evaporator coil. Ambient is, eh, 85F (it's hot where I am), you'll keep your ~33% solution at a setpoint of 27F, but you don't want your pumps or your evaporator to be on constantly, obviously. How do you size your reservoir appropriately to hit that sweet spot between capital cost (the cooler and pumps, sure, but also the glycol) and ongoing electrical costs? Obviously some of it also comes down to your system sensitivity and setpoints, the size of your pumps (i.e., your flowrates), etc., but are there assumptions or simplifications you can pretty much universally make (most of the heat is going to be coming from the environment, rather than the exothermic fermentation reaction, for instance?) to simplify the equations?
It's one thing to missize your mash tun - you just take the manifold out and put it in a bigger one and stick the missized cooler in your garage for picnics. But once you start cutting out holes to accommodate your twisted evaporator coils and drilling holes here and there for tubes, a cooler becomes a little harder to re-purpose, so I want to make sure I do it right!
Edit: Guess my primary question is about reservoir size, but I'm also interested in how that interplays with pump size ... obviously, if your reservoir's smaller, your pumps need to be able to pick up the slack, but that's only good up to a point (eventually, you're returning glycol that can't be chilled quickly enough for the extra pump power to be worth it). You'll need a certain amount of glycol and certain sized pumps for a certain sized reservoir ... transforming all that in to a cost equation, where's the minimum?