I’ve been googling for some better cooling and airflow solutions for some of my server racks, and came across this: VariCool Rackmount Fan Tray. This is a 1U device with a bunch of fans oriented horizontally. What is the purpose of this thing? Sitting between two other pieces of rack gear, there’s nowhere for it to draw air from or blow it to, unless I’m missing something fundamental.
I think I’m going to get something that makes sense to my meager brain, like this.
As you surmise, these are worthless for boxes with no venting on the top or bottom.
19" rack mounted electronics predate servers though. Many of the chassis have perforated tops and bottoms to allow convective cooling. The fan trays are meant to enhance the cooling of such, and are a good idea when you need to stack up several high power devices.
A few servers are top-vented as well. It’s quite rare, but I know I’ve seen some SUN server, I believe it was, that expelled its hot air through its roof.
Still, that fan doesn’t look like anything I would put in a server rack.
It used to be a popular MO to inject cold air under the raised floor, where it would escape through vents into the bottom of server enclosures, pass through the stacked units and escape as hot air to intakes in the ceilings. Obviously, this takes 4-post racks with solid doors to work properly, restricts the cooling effect on the topmost units and tends to fail for the racks furthest from the cold air inlets, so the concept has fallen on hard times.
The 1U unit in the link would of course be useful in this scenario.
These days, cold aisle/hot aisle is the preferred method instead, with cooling air moving laterally.