The power supply has a fan, it's just not visible. It *does* ventilate the air though rather poorly (the pictured end is the exhaust). The PSU is rated for something like 105C, so I wouldn't worry too much about *it* getting hot. Although some heat is radiated from the PSU to the heat exchangers / water radiators, it isn't a huge deal. If your cores are hitting 95C (the safety cutoff) than your ambient air temperature is too high, or your air circulation is poor.