How do you connect a TEC directly to the PSU?
 

I'm doing a project for school that involves a TEC unit. After reading around on the forums here, I've found that you can just connect the positive wire with either the 12V or 5V wire on the power connector. But my concern is with the current supplied by the PSU. The TEC unit I'm using is only 54.4W, with a Vmax of 15.4V and an Imax of 6A (numbers may not be accurate, this is just what I can remember). The power supply I'm using supplies 12V @ 12A. Would I end up frying my TEC unit if I just hook it up directly to the PSU without using any external resistors? The PSU will be totally dedicated to the TEC unit, so power supply isn't an issue here.

You should be OK, as long as you cool the the TEC of course.
At 12V the TEC should not be pulling anyware close to 12A if you data is correct.

It's quite hard to fry a TEC like that (unless you don't cool it - then it'll melt). You're more likely to fry your PSU if it's underspecced for the task. You certainly don't want any current limiting resistors on TECs as a general rule.

Thanks for the replies. Would a standard CPU heatsink be enough for a small TEC like the one I'm using?

depends on your heat load, but yes, I expect it will be able to.
At 12V you'll be sinking roughly 56W from the TEC, plus whatever the heatload is. Your Qmax at 12V is around 32W, so you shouldn't be sinking more than 88W, which is well within a reasonable CPU cooler's capabilities. The main issue is getting sufficient clamping force on a TEC with a standard CPU HSF isn't actually that easy.