The 'convector' style case

[twinbee]

I have at the moment a pretty silent PC. However, that may change when I buy a Fermi-class GPU. I've heard the thing puts out about 300 watts, so I'm anticipating I may need another tower case fan ON TOP of the standard PSU fan that's in there.

That got me thinking - why don't tower cases work like standard heat convectors where fresh air is drawn in from underneath, and then exits at the top of the case? Basically, there would a metal grill at the bottom and top. See this pic:


Simple physics right? Hot air prefers to go from down to up, rather than in from the side, swirl round a bit, and then exit via another side entrance. Am I'm missing something here? Why aren't all "cool" cases already doing this?

It wouldn't surprise me if we could eliminate case fans altogether by doing this.

[quest_for_silence]

I have at the moment a pretty silent PC.

Which is?

However, that may change when I buy a Fermi-class GPU.

Which one?

[Modo]

Silverstone makes cases that apply this principle: The Raven RV-02, and the Fortress FT-02—both reviewed here at SPCR. Take out the fans, and you have a basic fanless setup. Keep the fans, and even the most power-hungry components will stay cool.

As to why there aren't more of these. They are very big and expensive, and for a fanless rig, you need expensive parts that can handle very low airflow safely (and still you end up with underpowered graphics). This makes these cases specialist products for a small market.

Maybe a small box based on the same idea would be more popular. Think a cube with a mATX board on one wall, and all drives plus the PSU on the other wall. No, I haven't seen anyone making such a thing.

[twinbee]

Yes, it only needs to be a standard-sized case for most people. Personally, I'll be using an Intel quadcore (non-overclocked), Nvidia 9500 GT, along with an Nvidia Fermi 580 GPU (both for testing purposes), and a couple of 2.5" HDs (one of which is SSD), so I should be fine if I get at least it a bit cooler in there.

The two Silverstone models seem okay, though it doesn't look as though the whole of the underside and top are 'open to the air' so to speak. The fortress only allows a small slit of air which is I think is at the side bottom, and the whole thing isn't lifted from the floor by the looks of it. The raven looks to be at least partially blocked off at the top by the looks of it.

It may be a good idea to block the sides completely to allow for more of a flow effect from bottom to top. If there's nothing out there, maybe one could use an existing case, and modify it (steel cutters, and add feet to the bottom ) Though in theory I should be able to buy something off the shelf. That's if it's actually a good idea - and I think it could stand a chance of being a very good/simple idea, but maybe I'm missing something.

[Modo]

Yes, it only needs to be a standard-sized case for most people.

The standard size is achieved by cramming stuff together, and forcing hot air to move from one component to another. You won't get a small case while retaining good airflow. Note that the cube idea would mean doubling the case width.

The fortress only allows a small slit of air which is I think is at the side bottom, and the whole thing isn't lifted from the floor by the looks of it.

Yes, it is lifted--that's a solid piece of steel at the bottom, so no carpet would be obstructing airflow. This is a very large case, so the "small slit" actually has a bigger area than all the vents on most mid-tower cases. Enough to feed 3 18 cm fans. I recommend using some measuring tape to see how big this thing really is.

[Big Pimp Daddy]

Yes, this idea has been discussed before. As the whole "hot air rises" thing is probably the first bit of physics most people learn it's not exactly a secret. The problem is that the speed of the convective airflow depends mainly on the temperature, which in a computer case is still relatively low. The majority of fanless setups do utilise this effect, but as stated before, the airflow created is so low that it is difficult to cool components that produce much heat. As a good undervolted fan can create exponentially more airflow whilst essentially remaining silent (certainly quieter than a mechanical 2.5" drive), not many people choose to go completely fanless.
Of course, this being SPCR not QPCR, there are several people on here who have done this, my HTPC being one (though it is a VIA chip so produces little heat and can withstand the high temps it reaches on load), another notable example is maalitehdas here, but he uses a large chimney to boost the stack effect, creating more airflow.
By no means am I trying to put you off trying, that's how progress is made, but be aware that it is difficult, and has been tried by many before you.
If you are honestly trying to cool a quad-core and a 580 by convection alone, then I must advise you quit smoking crack, it's really bad for your teeth...

[twinbee]

Thanks, that's interesting, and glad to see it's been looked at.

If you are honestly trying to cool a quad-core and a 580 by convection alone, then I must advise you quit smoking crack, it's really bad for your teeth...

If I were to have it completely open-air (or a case with grills all round, mostly holes, more than metal), would that be enough to cool the quad-core and 580, considering that they of course have their own fans anyway?

[Big Pimp Daddy]

Ah, OK. I misunderstood you. I thought you were referring to removing all fans in the case and replacing CPU/GPU coolers with aftermarket passive ones for a true zero-fans case. Yeah a case with no case fans will work OK with convective cooling alone, in a well designed case or a very open one, or open on a bench. This is not ideal from a silence perspective as there is nothing to block the noise from the (normally noisy) stock CPU and GPU coolers, or from a maintenance perspective as there is nothing to block dust/debris getting into/onto the components. Also if you have pets or children this will end in tears.
As I said generally it works out better from a silence perspective to have even just one slow case fan, but feel free to experiment, it's the only way you will find the setup that works best for your particular situation.

[cordis]

Maybe a small box based on the same idea would be more popular. Think a cube with a mATX board on one wall, and all drives plus the PSU on the other wall. No, I haven't seen anyone making such a thing.

I did something like that in my homemade big brass box (viewtopic.php?f=14&t=59803). It's a lot bigger than what you're thinking, and it puts the components on that middle piece to keep the air from the different compartments mostly separate, but the principle is the same. It could be a lot smaller with an mATX sized board, although you'd lose some hdd space. It's really effective at keeping things cool, I have an i7 980x and a evga gtx 460 ftw in there now, and since I fold on it both of those components are running at full speed constantly, and both are overclocked. The cpu temp is in the mid 40s, and the gpu is hovering around 68C the last I checked. No idea what they would be if the fans weren't running, I suppose if I kept the bottom fans going and put an external heat sink on the 460, things might still work. Actually, I've been thinking of making a smaller wooden version of this case, maybe I'll get on that.