Perfect case size for best airflow?

[sim`on]

hi guys,

first of all i want to apologize for every mistake in this post, i'm german and a quite regular poster on http://www.silenthardware.de/forum (greetings ).
i'm posting because the discussion following a post of mine on silenthardware.de didn't quite satisfy me.

i'm going to build my own pc-case for my ABIT NF7-S, 2500+, 9800pro (as soon as i have the time...), and i am still looking for a concept. i want to reduce the number of fans to a minimum, and use 120mm fans only, if possible.

here's my question: what case size would be best for maximum airflow? as small as possible with the motherboard? as big as possible in my room? or something in between?

i have the idea, that the smallest case possible would bring a higher flow rate, than a bigger case with masses of "unused" air (with same fan configuration). wrong?

thx for every reader & answer

[sthayashi]

I voted: I have no idea.

This is because there are too many variables involved. Let's assume for a minute that the biggest case possible is no case at all. This often has the best cooling over a cramped space with a mess of wires.

BUT...... a normal sized tower case has been known to run cooler than open air, due to excellent airflow techniques. So the right answer is that it's somewhere in the middle of really big and really small.

[Tigr]

You should have another option for "the size of the case does not matter as much as you think". Sthayashi is right, there are many things at play here and you can have a bigger case with worse temps or a bigger case with better temps. Usually, the case is chosen for the convinience of either working in it or having it around. Well, I guess some also choose it based on aesthetics, but I would not have an idea... So, basically, I think the size as such plays a minimal role, far less than the design of the case. And I mean whether the case was designed for good airflow or not.

[Ralf Hutter]

So, basically, I think the size as such plays a minimal role, far less than the design of the case. And I mean whether the case was designed for good airflow or not.

Bingo.

[sim`on]

the design doesn't play the role here, because i make the case myself. the airflow design remains the same, big or small, as i will only use 1x 120mm case fan and 1x 120mm PSU fan. the air intakes should have the same size, too, no matter what size the case is.

the difference between big and small case, in my opinion, does influence the air flow though. in a big case, there is much more air that can take away the air from the hot parts, in contrary, i think, it's much harder to archieve perfect airflow in a big case.

?

[sthayashi]

the design doesn't play the role here, because i make the case myself. the airflow design remains the same, big or small, as i will only use 1x 120mm case fan and 1x 120mm PSU fan. the air intakes should have the same size, too, no matter what size the case is.

the difference between big and small case, in my opinion, does influence the air flow though. in a big case, there is much more air that can take away the air from the hot parts, in contrary, i think, it's much harder to archieve perfect airflow in a big case.

There is more to airflow than just the fan. There's static pressure and direction. For example, if you have a case with just one hard drive, you can get some very good airflow going. But if you put 4 hard drives in the front instead of one, your airflow can suffer greatly since the air has to go around the hard drives.

So if your case is designed like a wind tunnel, a smaller case would be better, but if there are too many things in the way, like Ram, PCI cards and hard drives, then a bigger case would be better, for the very reasons you described (more air in general).

There is a downside to a case that's TOO big. You could have static air, i.e. air that's not moving. This can be a problem in full tower cases where the PSU is NOT at the top of the case.

[MainframeGuy]

Personally I think placement of fans will matter almost the most relevant to heat sources and outlets... the one thing I can say with confidence is the larger the fans the better - so there must be room for 120 mm fans, and if you want to have serious air flow and minimal noise you may want a set of four of these running verrrry slow at the rear, maybe two sucking from the floor and one sucking at the front to vent HD - this starts to bring you dimensions, although how you array these fans is another issue and you MAY have no need whatsoever for such a serious air flow.... it's just your post read that way!

[Straker]

i'd say bigger, for the same reason a lot of cooling methods for overclocking are also good for being quiet (when they don't involve huge/fast fans), it just gives you extra overhead. a bigger case would normally let you organize cables/components better, give more leeway for suspending drives and mounting fans, easier to get air through it etc etc.
for the case by itself, sure, you can fairly easily get better airflow the smaller the case is - imagine a 120mm soup can with a fan on each end.

[pangit]

I voted #1, as I know I'd never be able to get the same amount of low airflow cooling as I've got in a cramped SFF/HTPC case. It's probably not impossible, but just much more of a challenge when you don't have much space to work with.

However I think it should be qualified with - "No way, the bigger the case, the better the temps - up to a point!" as has been mentioned by others that a really huge case (i.e. full tower or bigger) would not necessarily help. So for me there's a happy compromise - mid-tower case, which gives me plenty of space to work in but not excessive amounts of dead space interfering with airflow.

[sthayashi]

I voted #1, as I know I'd never be able to get the same amount of low airflow cooling as I've got in a cramped SFF/HTPC case. It's probably not impossible, but just much more of a challenge when you don't have much space to work with.

Imagine if you will though, an SFF case with no drives (say the drives are on the outside with magical wireless cables connecting them to the board ), but the front was an fan-sized opening in it, with another opening in the back with a fan sucking the whole thing out. Would this computer be warmer or cooler than a larger sized case doing something similar?

I believe it would be cooler. But ONLY in such circumstances.

[caber]

Not trying to be mean but.... will money be a concern for you?

you said that you are going to make the case yourself, so will a smaller case be cheaper to make..?? If you will be managing the wires and just "let it hang" I think medium towers are great because medium towers have some room for you to play (you did not say how many hard drives you have.. )

A cousin of mine has a AOPEN XC Cube, and the wiring for it is not too good and the temeperatures can be a bit high with 2 hard drives inside... No room to put the cables, too small of an area. However, he may reorganzie the wires and maybe the result will change.. Good luck

[sim`on]

I voted #1, as I know I'd never be able to get the same amount of low airflow cooling as I've got in a cramped SFF/HTPC case. It's probably not impossible, but just much more of a challenge when you don't have much space to work with.

Imagine if you will though, an SFF case with no drives (say the drives are on the outside with magical wireless cables connecting them to the board ), but the front was an fan-sized opening in it, with another opening in the back with a fan sucking the whole thing out. Would this computer be warmer or cooler than a larger sized case doing something similar?

I believe it would be cooler. But ONLY in such circumstances.

well, that was my question, thank you.
no, i don't have magical wireless cables, but cables can be organized, so i don't expect them to be a big problem (as you can imagine, i will not have any problems to drill some holes into the case for fixing cables with cable ties; round cables are already in use).

i'm thinking about mounting the harddrive in an "extra" section, so it doesn't take away any of the airflow necessary for cooling graphics & CPU.

as some had questions about the hardware:
- abit nf7-s (zalman northbridge)
- barton 2500+ (HT-101)
- sapphire 9800 pro (VM-101, perhaps i'll turn or bend it one or the other way...)
- Noiseblocker Fortron 350W mod w. 120mm fan
- Seagate Barracuda IV 7200, 80 gig (only hdd in the system, will be decoupled)

as i already wrote, my goal is to reduce the total number of fans in the system to 2 / 3. it's no option to place more than 2 fans into the system (though big and slow-running), because it wouldn't be a real improvement to my present situation
the question is, to repeat it once again, how can the airflow be maximized using only those two case fans?

i was going to place those fans next to each other at the back of the case (for obvious reasons), and the air intakes at the front. the design would remain quite the same, no matter what size i was going to use.

and, yes, it would be cheaper to make a smaller case, but money doesn't really influence the choice because i want this to be the only case i will ever use for this pc (i'm not planning to buy or build a new one after this experiment). of course, that's why it's so important to make the right choices from the start

[Tibors]

[...]the question is, to repeat it once again, how can the airflow be maximized using only those two case fans?[...]

You are still asking the wrong question. Nobody here will have this ultimate design for you. If somebody would have it, it would already be posted in the General Gallery.

The question of the poll is already answered several times. Size alone does not really matter, design does. Some designs will need a large case. Some others will fit a smaller size.

What you should do is; just create a design. You can find plenty of idea's around these forums. Combine them into something you think is ideal. Then post your design, so everybody here can give his thoughts how to improve your design.

What you should look for is:

• Not too much obstacles in the flow path.
• Not too much (sharp) turns in the flow path.
• If you're using filters, enough filter surface.
• Fans in parallel are generally more effective than fans in series.
• Hot air rises, so exhaust above intake is more effective as vice versa.
• Everthing else I forgot to mention.

[Spod]

I agree with Tibors - we'll be able to give better advice if we're tweaking a design you've posted, than trying to design something from scratch ourselves.

Also, don't forget the hard drive would benefit from some cooling as well.

[pangit]

Based on your hardware set-up, you should be able to do what Bluefront has done with his HT-101 and 120mm fan PSU - duct the CPU air into an enlarged (and thermally isolated) PSU box with a single fan, which has been proved to work. Then you only have the video card and HDD to think about.

how can the airflow be maximized using only those two case fans?

I think the answer is to maximise the efficiency of the fans, by using one as described above, with the other one perhaps taking care of the HDD and video card (tricky I know )

One way to approach your whole "how big should I build the case" question is to lay out all your components on a table (or on paper/CAD) in various different configurations, and see which makes best use of airflow running over the hot components (using one or two separate air paths). Then build a case around that, whatever the size is. I believe you will end up with something approximating a mid-tower case in size, even though the layout may be different.