Hello Jacob,
yes I use one of the exact items you are interested in.
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After use, I flush it through the wort pipes in both directions with a garden hose flowing briskly. I drain the water and then refill with mixed Starsan solution and cover the outlets with aluminium foil and store until next use. Next use I tip out the starsan and will run a bit of hot wort through it before I turn the cooling water on.
I bought one of these plate chillers because I thought it was neat that it has 1/2" NPT female sockets in it to attach whatever fittings I desired. It is a reasonable unit.
However, I think (but I could be wrong) that it appears to be no different to countless plate chillers/ biodiesel heat exchangers on eBay.
I have also seen a mashmaster plate chiller in the flesh and it is a much longer and sexier item. I now have mashmaster plate chiller envy. It has barbed fittings on it but I don't think this would be a problem. I have used camlock fittings etc but am sort of moving back towards barbed fittings or some type of quick disconnect that I have not yet tried.
As for the flow rate of the plate chiller under a gravity feed, I can whack 25L through in a couple of minutes, it doesn't strip much heat out though with garden hose water around 20oC. I think it pulls the wort down to about 50oC if I run through slightly slower than flat out, maybe 70oC if flat out. That's quite fine if you just want to knock it down under hop isomerisation temps. I sometimes do this and return it to the BM for a much longer whirlpool and settling out time period. Then I run through the chiller quite a bit slower to reach about 24oC which is the best I can get without prechilling the cooling water.
I haven't really got prechilling the cooling water down pat yet. Submersing the chiller in cold water wouldn't really work very effectively unless you could circulate the water around the chiller unit and there appears to be better ways to do it. I'd suggest you pass the cooling water through your old immersion chiller that is placed in a container of ice slurry that is heavily salted. I'd reccommend a flow through temp guage of some sort to monitor the temp of your chilled wort pre-fermenter. It would be best to have valves on both the cooling water and wort outlets to regulate the flow, to control temps.
Just my 2c and I am sure you will get other ideas AND better ideas.