Given the heatload (thanks to Since87) I'd try this out with smaller tubing than 1/2: 1/4 ought to be plenty.
As for cooling the coils (aka inductors, aka "doughnut shaped component"), there is no standard solution (that I'm aware of): the very nature of the coil doesn't give you a surface to mate a heatsink.
BladeRunner however extended a copper "arm", which was thermal epoxied to the top of the coil, in his PSU water cooling project.
If you go that route, you need to know this: the wire that is wrapped to form the coil, has a varnish coating on it, so that it's not just one "blob" of metal; the curent actually "turns" round and round. That varnish is easily scratched, exposing a live wire.
