(NVIDIA) Fan-Based-Heatsink Designs are probably wrong. (suck, don't blow ! heatfins direction)

Additional:

Since my horror experience with the 7900 gtx cards I am afraid to buy graphics cards with the nvidia heatfins direction.

I am afraid that the graphics cards heatsink fins will get full of dust and stop to function !

My newest passively cooled graphics card is actually also an nvidia/asus design. Where the heatfins are in the direction against the airflow.

So far there is probably no dust in side of it... or very little... which seems to be much better.

If nvidia wants my bussiness back they will have to design cards which can operate for the long term, without requiring any cleaning what so ever.

I am not going to open up my PC and risk damage during cleaning operations.

NO CLEANING operations should be necessary.

THEREFORE nvidia must design graphics cards which will operate for a long time... 5 to 10 years of blowing/sucking air.

Perhaps the heatfin direction that I proposed is less optimal in the short term... but will probably be optimal in the long term.

Therefore my advise to nvidia which they hopefully already have:

1. BUILD A DUST/PARTICLE LAB.

1. TEST the graphics card heatsink design for as long as possible... and test the situation with dust build up.

2. Build the graphics cards which has the least problems with dust build up.

Otherwise you can go to hell... I do not ever want to face overheating problems because of gpu overheat/heatsink full problems ! ;) :)

Bye, Skybuck.

One last explanantion/addition for any potential dumbos out there to explain the "suck, don't blow" part of the title.

The idea is to:

BLOW air OVER heat fins.

Hopefully this will create some kind of suckage effect over the heatfins and suck heat from between the heat fins and blow it away.

This might also have a beneficial effect of sucking any dust/hair particles out of it and blowing it out.

That's the idea at least... which would be very nice.

I am not sure if it will work like that in practice... since there is no opening on the other side of the heat fin to suck from....

So maybe some kind of vacuum would result from it...

If that is a good or bad thing remains to be seen/tested.

Very maybe openings could create on the other side... but that would probably start to suck dust between the fins which would be bad.

So experimenting with this idea is required to see what works best long term.

My only worry would be that the opposite might happen, maybe dust will start to fall down between the heatfins....

What will happen in reality I don't know...

THIS REMAINS TO BE TESTED ! ;) =D

Perhaps someday... a dust particle simulator might show what happens ;) :)

Bye, Skybuck :)

You are an idiot.

They suck so that YOU still have direct access to clean the tines of the heat sink. If they blew, the heat sink would get plugged up in a place under the fan, and you would have to remove the fan to clean it.

Now shut up and go away and stop making posts which you are then the only idiot who responds to it the first 5 times!

Grow up, child! You are immature AND stupid. Get over it. Leave US out of it.

You are a very particular type of Usenet idiot, and you are blind to it.

And reduce the chance of getting heat out of it.

Even better, aim the fan at something else a foot or two away.

You are of course assuming that you know more about cooling a CPU than all the people who currently make a living cooling CPUs, including the MEs in charge of thermal design at Nvidia.

I have this theory that the fins of a heat sink should reduce a fan's free-flow rate by 50% for optimum heat transfer.

Unless chambered to stop air flowing in for an arbitrary 10-25% reduction of motor shaft speed, equal to chambering outflow, or both chambered, as opposed to an effective vacuum, which might further indicate where motor design is outside operational efficiency, irrelevant of equipment MTBF, and provided there's salience to some residual mean temperature for cooling to be a factor in coincident significance to ascribe at the proposed structural end as an operative upon RPM.

Umm, you would not perchance be employed in a government position (spin doctor) ??

optimum heat transfer? not sure what the criteria would be, but think instead about the air's thermal mass, thermal resistance form metal to bulk air. and you see you're left with characteristics of the heat sink, not the characteristics of the fan.

As a mind argument enfisionone hell of a powerful fan. Now block that to half flow, what do you have? versus an 'underpowered' fan that is blocked to half flow. .

When a video driver installation takes 200 MB on a hard drive and is still full of bugs, there is every reason to question designers' competence.

DK

ER

The reason the heatsink _has_ fins is to maximize the contact area between the heatsink and the air. So you also want to maximize the velocity of the air in proximity to every part of the heatsink, so that there is a larger temperature difference over as much of that large contact area as possible.

One puts a dust filter in front of the intake vent to keep dust out of the fins, although dust generally does not collect where there is a violent wind.

What you really want to do, though, is use a working fluid other than air which can carry more heat away. Of course, the Montreal Protocol because of the ozone layer makes that more complicated; the other alternative requires careful precautions because it becomes electrically conductive very easily by dissolving material.

But a third alternative to setting up a refrigeration system and using chilled water would be using chilled mineral oil. Of course, there, flammability is a problem, although the fractions typically used for such purposes aren't too bad...

John Savard

That's a different group of engineers. I doubt seriously if the design engineers are also the software engineers, although there is probably *some* collaboration between the two groups. The design engineers I worked with had a motto: "If it ain't broke, redesign it!" No such thing as leaving well enough alone :-)

En el artículo , DK escribió:

Come on. That's software vs. hardware. The engineers may design and build superb hardware, but if the software isn't up to scratch, it's wasted effort. Look at ATi/AMD cards, for instance. Good hardware, lousy drivers.

If I had my druthers, I'd as rather gainfully, that is contractually and under government auspices, to be on your tax dollar, sic, whereby to impose mandatory interpolation of required observances, forthwith said forthrightly, such that as an agreeable conscientious citizen, I'm sure you are, there could be no other possible meaning given you to mistake my greater schemes.

-- 'Within a judicial system, the only worse case scenario, other than a divorce, is a lawyer in full possession and faculty of doctorates both in law and philosophy.' -Socrates, A Known Drinker of Hemlock

Right.

Minimum theta would do.

but think

If the heat sink doesn't reduce air flow at all, the air is going around the fins, not through them (as Skybuck suggests) and the air does no good. And if you block all the air flow, it does no good. So the amount of airflow restriction that results in the lowest theta must be somewhere between those two extremes. Dead center is a pretty good guess.

I realize that. Just couldn't resist. Plus, I think it points to some fundamental management/business philosophy problems that are very likely to influence all layers in the company, harware included.

DK

If the input and output temperatures were the same, that might be true. It might also be true if you consider the reduction in free flow rate caused by the back pressure due to the head sink obstructing the air flow.

However, air expands when heated, causing an increase in air flow at the exhaust end. That's why the exhaust port for a heat removal system is larger than the intake. My guess(tm) is that the increased exhaust air flow caused by heating is much larger than the reduction in intake air flow caused by the fins getting in the way.

On the original assertion, that it's better to suck than to blow, methinks that's wrong. You can demonstrate this with a dirty computer. Take a vacuum cleaner and try to remove the dust by sucking. Most of it will still be in the machine when you're done. Now, put the hose on the same vacuum cleaner exhaust and blow the dust out of the machine. Notice that remaining dust is effectively blown all over the room.

It's dispersion versus concentration. When sucking, one pulls air from the sides and from all around the heat sink, including air that does not need cooling. This makes the fan work harder moving excess air, leaving less air flow for between the heatsink fins. Turn the fan around and blow air at the heat sink, and the entire air flow is involved in cooling the fins.

Similarly, you can demonstrate the effect by comparing the CPU temperatures with the fan in the normal position (blowing air down towards the heat sink), versus flipping the fan over and sucking air out. I did this with a Pentium 4 dual core. I forgot the measured temperatures, but the difference was substantial.

What you want is immersion cooling:

Build a leak proof package, insert computer, fill with fluorinert, mineral oil, anti-freeze, distilled water, or whatever and it will redistribute the heat to a much larger mass and surface area.

Given the same mass/sec flow of air over the fins of a heatsink, the best heat transfer is by blowing due to the greater turbulence - which disturbs the boundary layer of air that lies in contact with the fins and puts more flowing air in direct contact with the surface of the fins. In the case where the fins rise up away from the source of the heat, it's best to blow downward from the ends of the fins toward the source of the heat. IOW, the air should move in a direction opposite to the heat flow.

This principle is not only used in heat transfer systems, but also in biological systems in oxygen transfer through membranes - as in fish gills where the blood moves across the gill membrane in a direction opposite to the flow of water. The basis of this principle lies in the finite heat (or gas) capacity of a fluid and that greatest heat (or gas) flow occurs as a linear function of the difference of temperature (or gas concentration) between 2 bodies. Apply a little calculus, and the principle of opposing flows results. This design principle was recently seen when I opened up the case of a friend's PC to clean it out: The cooling fins for the CPU rose up from the CPU, and the cooling fan blew air down along the fins toward the CPU. Obviously, the designer had paid attention during college freshman physics.

Oddly, my new, stock heatsink is designed with fins arranged not-quite-radial, in an X pattern around the center. It looks like extrusion oriented axially (axis normal to the processor face), rather than transverse. The fan blows air over the center and fins.

At 100% CPU I get 42C tops, so it seems to be doing its job. Nothing special, a dual core 3.2GHz Athalon II. It's also entirely possible AMD (or whoever they contracted to make them) doesn't know their physics.

Note that heat transfer by volume isn't usually the goal, so much as minimum temperature is. In a counterflow setup, the hottest part of the heatsink is cooled by the hottest air. If you flip it around, the hottest part of the heatsink gets cooled by the coolest air, achieving the highest heat flux for a given surface area and temperature difference -- more power density, at some expense to mass flow and pumping loss. You might avoid this, for example, if you had to use pure nitrogen (or helium, for that matter) for some process, minimizing the gas flow to keep operating cost down.

Tim