[dimmreaper]

Many of the concepts of waterblock design carry over. For example you want lots of turbulance and surface area, however you want to get more in to a smaller space as the liquid doesn't remain a liquid. You also need to keep in mind that soldering joints need to be a little larger as you are dealing with more pressure, the use of silver solder is highly advisable. Best bet is to keep it simple, start with something like Surlyjoe's beehive design and modify as you see fit for phase change.