Resistance on heat sink fins???

[Arun81]

Dear all,

I am working on a liquid cooling system and have to deal with resistance on base,fins and fluid flow. I found the traditionally used equation for fin resistance doesnt have any dependance on fin materials thermal conductivity. Isit that if i use a plastic fin which has a very low thermal conductivity will not affect the overall heat transfer? I see only the huge dependance of materials thermal conductivity on base resistance. i tried to make a analytical tool with excel and found out that the resistance of fin is not changing much with change in the fin material. But in a broader look we can say that if a fin matreial is plastic there wont be a good conduction of heat to coolant. Please provide your guidance on this..

thanks in advance

Arun

 

[IRstuff]

The only case where I can see this as a plausible scenario is if there is some sort of weight criticality.

Given that you would have a required delta temperature between ambient and junction temperature and a fixed power dissipation, a metal heatsink will provide the most efficient solution for a given cooling capacity.

Any plastic solution, simply by virtue of its poorer thermal conductivity, must result in a larger heatsink to provide the same cooling capacity. Since people don't make plastic heatsinks in general, you're going to incur cost for the development of the molds or extrusion dies, special handling of non-standard parts, etc. You're going to be limited in the number of suppliers, since a metal heatsink could probably be readily copied by any heatsink supplier, but a plastic heatsink will have to go to a specialty plastics supplier and changing suppliers will result in a new learning curve.

Note also, that the dimensional stability of metals is much better than plastics and many designs have relatively tight dimensional requirements in placing the parts against a heatsink while being installed on a board that's mounted with the heatsink.

TTFN

 

[drkillroy]

Hi there!

I'm courious about reactions between the heat sink and the fluid used to transfer heat. Plastic would, I believe, be much less reactive than aluminum. Automotive applications see white powder corrosion even related to the cooling system running antifreeze. Also a jell of some kind build up on the aluminum surfaces. Can this problem happen in the application discussed here?

Thanks PZas Your post was quite helpful!

drkillroy

 

[IRstuff]

It's precisely the antifreeze that causes the problem. Ethylene glycol is actually corrosive.

TTFN

 

[drkillroy]

WOW!!!!

What fluid with a low freezing point (near 0 degrees F.) that can conduct and carry a large quantity of heat per pound mass can be used that is not reactive with copper and aluminum (not in direct contact) within the same system? I'm mentioning copper as well to cover other potential problems.

Thank you Drkillroy

 

[IRstuff]

you can still use either EG, PG or Fluorinert.

TTFN