Ask Dan: Which way up for motherboard heat pipes?

Date: 17 February 2007
Last modified 03-Dec-2011.


So, do these motherboards with heat pipe coolers - like the Asus P5N32-E SLI Plus - really not function properly on inverted cases such as the Lian Li PC-V1000? I am getting conflicting viewpoints through my Googling efforts.


The most elementary kind of heat pipe is just a sealed tube made from some thermally conductive substance, containing a small amount of a liquid that'll boil and condense at appropriate temperatures for whatever the cooling application happens to be. There are more requirements for a working fluid, which I talk about in this column, but those are the basics.

This kind of heat pipe will, indeed, only work when the hot end is down and the cold end is up. It won't work when it's upside down, and it'll only barely work if it's horizontal (or in zero gravity). If it's a bent pipe, any portion of it that's asking the condensate to flow uphill will cause problems.

To get around these problems, the vast majority of heat pipes, including all of the pipes used for PC cooling, have a wick around the inside of the tube that draws the condensed fluid back to the hot end by capillary action. Wicked tubes don't work quite as well when they're hot-side-down as unwicked tubes, all other things being equal, and they also still work marginally worse when they're upside down. But that difference is nothing to worry about; it's likely to be quite difficult to even measure, if all you've got to do it with is motherboard temperature sensors.

So no, there's nothing to worry about with heat pipe cooled motherboards, or heat pipe CPU coolers, either. This is just as well, of course; if these things used wickless coolers then not only would upside-down-board tower cases be a bad idea, but so would desktop cases.

The advantages of heat pipe motherboard cooling are considerable. Apart from the unquestionable pose value of all those shiny pipes and fins, a properly designed heat pipe can take heat from more than one component to a single large radiator, which makes it easier to cool things like voltage regulators (which're otherwise cooled by conduction through the motherboard itself).

And, importantly, piping heat from mobo chips to good-sized fanless coolers in sensible places does away with at least one tiny little fan on each motherboard.

Those tiny fans never bloody last, in my experience. If you change your motherboard every year, then with any luck you'll only have to replace about half of the little fans when their bearings fail. If you keep your computer for longer than that, and it's on for most of every day, then a motherboard cooler fan is practically certain to die.

You may or may not be able to put another little fan on the existing motherboard chip cooler when one fails. The coolers are usually removable and replaceable with after-market ones, but it's seldom easy to get them out without removing the whole motherboard from the case.

If that prospect doesn't appeal...

+2 Fan of Dodginess

...then alternative solutions may suggest themselves.

My current computer's been running like this for many moons. The video card doesn't seem to mind the fan that's Blu Tacked onto it, but it's still not what you'd call an optimal solution.

Heat pipes, in contrast, have no moving parts and don't wear out. It's possible for them to leak, but they seldom do, especially in the relatively mild environment of a computer.

Heat pipes on motherboards are at least partly for show; there's room for larger aluminium passive coolers on the chips, which could probably do the same job cheaper. But the heat pipes do still do something useful, and should keep doing it no matter which way you point them.

Shoppers from Australia and New Zealand can buy the Asus P5N32-E SLI Plus from Aus PC Market.