Re: What's better, extruded heatsinks or machines heatsinks?

Hi,

All else being equal, it's the flatness of the mounting surface that
matters. If the heatsink surface is bowed, then the gap between the
drive and the heatsink must be filled with heatsink compound. Though
much better than air, its heat conductivity is much, much less than
aluminum.

You can always machine the mounting surface of an extruded heatsink
flat.

You want to keep the temperature difference between the drive
mounting surface and the heatsink low (1 or 2C).

The purpose of the heatsink is evacuate heat from the drives and dump
it into the ambient air. This means you want to replace the warmed
air around the fins with cool air.

Convection cooling depends on the fact that warm air rises and must
be replaced by cool air. To maximize convection, mount the heatsink
fins vertically to form a chimney.

Heatsink efficiency is greatly improved (100 times or more) by having
a small fan to speed up air replacement. The fan replaces the air
much more rapidly than convection. The air gains less temperature
before it is replaced, so the heatsink is much cooler as well.

Look at the size of a CPU heatsink/fan combo. A CPU can generate
twice as much heat as the drive ever will, yet the heatsink is very
small. The notches you see front and back on our drives are meant to
take a 50mm CPU heatsink mounting clips.

Mariss

--- In CAD_CAM_EDM_DRO@y..., "Lloyd Leung" <lloyd@l...> wrote:
> I'm wondering what's a better heatsink for my geckos.
>
> Assuming that both heatsinks are aluminium with same number and
size of
> fins, with same sized base, which is better?
>
> I'm just talking about heat dissipation, not costs.