Is it safe to leave an external hard drive that is only enclosed in an aluminum case with no fan?

I have a laptop that is pretty much a desktop replacement. For extra storage space, I decided to buy an internal hard drive and use a Aluminum external enclosure. However, after being warned by a friend that these may damage the hard drive, I looked up all over online to see if it really did hurt the hard drive. All the results are conflicting and I was wondering if it was a good idea to leave it on all the time as I back up files on a regular basis with this hard drive. So, question is: is it safe to leave this on all the time? If not, should I get another external case? Which one?


Is it safe to leave an external hard drive that is only enclosed in an aluminum case with no fan?
As long if its an external case is for only 1 hard drive you should be fine, the ones that hold more then 1 you should worry about having a fan for. Because just 1 hard drive will distribute its heat to the aluminum casing keeping it at a suitable temperature. But with more then 1 hard drive, one hard drive can give off heat to the other and vise verse, requiring a fan to keep them at a suitable temperature.Is it safe to leave an external hard drive that is only enclosed in an aluminum case with no fan?
You could leave it on, I would just put a heatsink on it. Buy a CPU heatsink and just clamp it onto the drive. This should do the trick, but it will look terrible.