coanda effect
Cray hit this problem many many years ago - when chip densities and hence temps were lower than today - they solved it by using evaporation.
At the time the engineers rather than try and design a customer injector assembly simply went to thier local motor parts suppliers (a lot of dealers in the MSP area) and asked for a range on injectors. Tests showed a certain Porshe injector created the perfect sized coolant droplet for the big cray boards.
To promote this breakthrough, Cray bought a load or "porsche" sunglasses and had Cray etched on them! very cool!
Oh and the other advantage of evap tech - no need to drain etc - you simply pull the boards and replace.