Need opinion on a heat sink (concept)

silent_hunter

Hello, I want to share a very simple concept with you guys. Last night I randomly modeled a heat sink [the fan is coupled with a motor,cool air will be supplied separately(details are in the picture)], now please give your opinion on it. Will this system work? I don't know if this type of mechanism is already in use or not.
thank you.

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justsomeguy

The only problem I see is that the contact area of your heatsink with whatever it is supposed to be cooling is very low. This is why most commercial HSFs (heatsink + fan) have a solid base. The more contact area you have to carry heat away from the device and into the fins/pins, the better.

This design would probably not work for a CPU since most of the heat is generated right in the center, where you have no contact at all, and the integrated heat spreader is a simple thin aluminum plate.

Some older video cards do have a design like yours, with the fan embedded within the heatsink, but they too still retain a solid base below the fan.

silent_hunter

thanks for your reply.
So according to you may the cooling rate be improved if I reduce the size of the fan and increase contact area?

justsomeguy

What are you trying to cool? Is it a solid square object directly below the fan? What is it made of?

silent_hunter

lets say its a hub sink made of Aluminium,I mean it cools multiple heat source perhaps by liquid cooling or like this one below (can be used for other purposes too)

(taken from http://www.hothardware.com/articleim...LC_3Dmodel.jpg)

justsomeguy

I ask because it matters how the heatsink interfaces with whatever it's primarily cooling, be that a hot surface like a CPU heat spreader, or water block, or whatever.

Not knowing that, my suggestion is not to shrink the fan (though that would help) but to put a solid base below the fan -- get rid of the 'hole' the fan blows through, presumably onto something hot that needs cooled, and get that hot thing in touch with the metal of your heatsink.

Like so:



You can cut a hole in the fins to put the fan in, but that's reducing the surface area that the air can move over, so you need to compensate with a higher CFM fan. That may not even be enough depending on the thermal coefficient of whatever you're building the HSF out of. Best to just slap the fan on top, in a shroud, like everyone else does (for good reason) ;)

silent_hunter

got it ,thanks.
one thing, Can outward flow of cool air below the fan(3rd pic of my 1st post) create disturbance for the fan(since air forces blades on the opposite direction of its rotation) ?

justsomeguy

This is similar to what you're proposing, maybe it makes it more clear. Whatever you're trying to cool needs to have it's full surface in contact with the heat sink material. You also want to block axial flow through the fan to ensure all the air is pushed around heatsink vanes and not just into some material it can't effectively cool.



Image is from an old low-power graphics card HSF. The other two heatsinks are passive coolers for the DRAM.

A clearer example:

silent_hunter

got it ,thanks.
one thing, Can outward flow of cool air below the fan(3rd pic of my 1st post) create disturbance for the fan(since air forces blades on the opposite direction of its rotation) ?