My solution for using trays like these is to leave the top off of them, and leave the bay above them empty. Like BreakApart says, they mostly dissipate heat through the top of the drive, and this allows plenty of that dissapation without the need for a fan.
I HATE noise, and so deliberately run low-powered setups (e.g., small die size intel chips, low wattage video cards and burners) in big towers with lots of room to keep case temps down and minimze fan use. So far, this combo has kept me from problems, even with 7200 rpm drives.