Bit more info:
I've got a 2" cube I built out of plexiglass. In the top of the cube, I put 1 hole for mounting a 1/2" hose barb dead center. In the side of the cube on one face I put 1 hole for mounting another 1/2" hose barb dead center. In the bottom of the cube I cut a hole approx 1/2" x 3/4" (just big enough for my XP core to fit in).
I got a piece of 1/2" copper tubing about 1 1/2" long. I also got a thermocouple for a central air unit ($2 at Lowe's), and cut it into 3/4" sections, so that I had a bunch of tubing roughly 1/16" ID and about 3/16" OD. I took 8 of these and arranged them into a 2x4 grid. I took the 1/2" copper tubing, smushed one end until it was just large enough for the thermocouple tubing to fit in, and then brazed the whole mess together into an assembly just a little over 2" long. I then took the tubing assembly and attached it to a 1/2" plastic hose barb (basically, I heated the tubing and melted it into the end of the hose barb). I then dry fit the assembly into the cube, aligned the end of the thermocouple tubing so that they came out where the core will sit. After that, I took it back apart, cut the tubing flush with the inside edge of the bottom of the cube, mounted the assembly, and attached the side hose barb. The result is an assembly the squirts water directly onto the
cpu core from a distance of about 1/8" (about 3 mm) using 8 1/16" (about 1 1/2 mm) jets, and then the water is evacuated out the side hose barb.
I've tried a number of different approaches to this problem, and this has worked the best of all, but I'm still not getting the kind of results that I had hoped for. A good standard water block will out-perform this setup, but I've seen articles where people have gotten MUCH better performance than this from
similar CPUs.