I'm a long time lurker here on AHB, this is my first post so go easy!
I've always been told that the slower the sparge the better. John Palmer says here:
The wort should be drained slowly to obtain the best extraction
I have myself a HERMS electric brewery and to maintain the mash temp and ascend temp to mash out, I find I need to recirculate the mash quite quickly. Perhaps 60% - 70% the capacity of the chugger pump. Perhaps 2 - 3L of wort per minute in a standard 15 - 16L mash. I measure my mash temp at the point where it comes out of the mash tun.
My question is, if I recirculate continuously at 2 - 3L of wort per minute, what would be the need to slow down that rate of flow when sparging?. I can visualise, for a static mash, that slow flow would be best, but I can't see how it would matter for a recirculating mash as you are constantly rinsing the grains.