Hi PhysicsForums. I have a question. I was looking through a manual for an industrial grade PC, which is fanless, with the CPU mounted directly onto the chassis which is practically one large heatsink. When considering side-mount applications for this PC, I noticed that the manual had a picture of the PC being mounted with the heatsink fins running horizontally, rather than vertically: I thought - surely convection would be much more effective if the fins were running vertically, then cool air would be coming in from the bottom and escaping from the top: ...otherwise the air would have no obvious path of escape: ... or is the difference between the two side-mount orientations negligible? Thoughts? Obviously sitting flat is the optimum orientation, but I'm just considering the wall-mounting options here.