I posted this link in reply to a thread below but I wanted to also post it here for reference. I like this forum and I think it can be a great resource for those of us working on a phase change project, it just needs a little jumpstart!
Here are SERIOUS hardcore component sizing calculations. The application is very similar to ours:
http://home.attbi.com/~prithabrownin.../chiller1.html
The part I'm having a problem with is that he does his system capacity calculations based on the weight of the coolant instead of the heat load in watts like we do our calculations. I guess his tank really doesn't have a heat load on it - just ambient temperature, so we have an added complication that he doesn't need to work into his system...still working on this.