Unconventional custom loops. The radiator's original purpose was to absorb about 7kW of thermal energy inside an air handler with a 40⁰∆.
In other words, an evaporator coil for a mid sized house.
It now dissipates about 700W with about a 10⁰∆.
Full flow, no real loop restriction as the ID is about 1/2"
The whole system will run passive (aside from the pump) during desktop use and 6 140mm fans spool the whole way up to maybe 800rpm while gaming.
In the winter this is the only heat source for the room; in the summer it's on tracks to slide outside the window so it doesn't get too warm.
In winter when I do slide it out I'm able stay under 20C under full overclocked load and have to stuff paper towels around the sockets for condensation. Super fun.