Positive pressure vs negative pressure

[Troika]

So, the more I think about the amount of potential heat, the more I think that the typical way I orient my fans may actually cause worse cooling performance.

Lets take a Corsair Air 540 as an example. In my configuration, I need a 360mm radiator to cool a vega 64 (full cover block) and a 280mm radiator to cool the processor, currently a 6600k.

Normally I orient the fans in this way. Front fans suck air into case. Top fans blow out, rear fans blow out. Because of the front radiator heating up under load, I don't think it'll be beneficial to have hot air going into the case and then through another radiator, which would also be hot, plus the heat from the vrm heatsinks. I'm thinking, rear fan sucks air in, front and top exhaust so there isn't as much hot air raising the ambient temperature of the case. My room is pretty well air conditioned so I don't expect the room ambient temperature to rise more than 1~3C at most. Ambient temp is about 22~23C. Or am I just overthinking it and it won't make a bit of difference.

[WoodenMarker]

More warm air as intake is generally better than less slightly colder air. What you already have is fine. 

[Troika]

Wouldn't the vacuum effect of the negative pressure pull in enough outside air to compensate?

[Neo-revo]

18 minutes ago, Troika said:

Wouldn't the vacuum effect of the negative pressure pull in enough outside air to compensate?

vacuum effect pulling dust in would only be a concern to me if CFM out >/=CFM IN(rad)  since the teory in air movement (plainly) max rpm= CFM add rad resistance(-20% made up number )  So if it moved 100 then after the rad it would only move 80..  now thats why we all have 'high pressure fans'  that help mitigate the rad fins resistance.

 

If CFM out greatly outweighs CFM in you will get air coming in the wrong spot to compensate.

 

all the air will still be moved, just not how you may like, (also consider resistance of dust filters/not cleaned ones, or just not cleaning in general. (i was surprised how dusty my 240 was on the bottom even with filters/regular cleaning  it was almost choked (certainly causing loss of performance )

[For Science!]

2 hours ago, Troika said:

So, the more I think about the amount of potential heat, the more I think that the typical way I orient my fans may actually cause worse cooling performance.

Lets take a Corsair Air 540 as an example. In my configuration, I need a 360mm radiator to cool a vega 64 (full cover block) and a 280mm radiator to cool the processor, currently a 6600k.

Normally I orient the fans in this way. Front fans suck air into case. Top fans blow out, rear fans blow out. Because of the front radiator heating up under load, I don't think it'll be beneficial to have hot air going into the case and then through another radiator, which would also be hot, plus the heat from the vrm heatsinks. I'm thinking, rear fan sucks air in, front and top exhaust so there isn't as much hot air raising the ambient temperature of the case. My room is pretty well air conditioned so I don't expect the room ambient temperature to rise more than 1~3C at most. Ambient temp is about 22~23C. Or am I just overthinking it and it won't make a bit of difference.

Depends on the case but in small cases likebmy define c doing what you describe improved temps substantially. Reheating thr case internals is a real phenomenon in my opinion.

[Troika]

2 hours ago, Neo-revo said:

vacuum effect pulling dust in would only be a concern to me if CFM out >/=CFM IN(rad)  since the teory in air movement (plainly) max rpm= CFM add rad resistance(-20% made up number )  So if it moved 100 then after the rad it would only move 80..  now thats why we all have 'high pressure fans'  that help mitigate the rad fins resistance.

 

If CFM out greatly outweighs CFM in you will get air coming in the wrong spot to compensate.

 

all the air will still be moved, just not how you may like, (also consider resistance of dust filters/not cleaned ones, or just not cleaning in general. (i was surprised how dusty my 240 was on the bottom even with filters/regular cleaning  it was almost choked (certainly causing loss of performance )

I tend to keep my room fairly clean but then again, I have carpet and that tends to attract dust like a magnet. I do use fine mesh filters to mitigate dust buildup on the internals. I clean the filters every two to three months, depending on the buildup and clean the inside of the case and radiators every six to eight months, depending on how much actually got in. Dust isn't a huge concern since even when I shrug off cleaning the inside of my tower for a year, there's only a thin layer of dust, most of which is on the fans and not the the radiator itself. Most of the dust is on the filters I use.

[Troika]

1 hour ago, For Science! said:

Depends on the case but in small cases likebmy define c doing what you describe improved temps substantially. Reheating thr case internals is a real phenomenon in my opinion.

I'm used to using larger towers so the standard way of setting up intakes and exhausts work well with positive pressure but I'm looking at moving to a comparatively smaller case and typical fan orientation may cause increased heat to buildup on components, which I don't want. A Vega 64 is a pretty hot card and I plan on pushing it as hard as I feel comfortable with, trying to keep temps at 60~70C max, hence why I'm wanting to put the larger 360mm rad on that and the smaller 280mm rad on the processor. I'm sure that a 360mm is overkill, especially with either EK Vardars or Noctua NF-F12 IPPC 3000s but I won't have a monoblock for my board, which means I still have to fall on air cooling for the vrms. I want to get as close as I can to a stable 5ghz on my 6600k, 4.8ghz may be a more realistic target though.

I do like the Corsair Air 540 and it still have two 5.25" bays for either fan controllers or if I decide to move to a full custom loop, room for a 2 bay 5.25" res. The plan currently is to keep using my H110i GTX for cpu cooling and picking up a 360mm MLC kit with a full cover block from EK-WB. Whether the plan pans out or not is a different question. I have to take care of the situation with my laptop first but that's neither here nor there at the moment. I have to wait for AVAdirect to get back to me.

[Neo-revo]

7 hours ago, Troika said:

Most of the dust is on the filters I use.

thats good,  and you do a thorough cleaning once a year is decent too,  when i discovered the 240, it was cause i was doing system maintenance, but with 2 year old fluid, (and only cause i wanted to mess with rad placement inside my case again)

 

If you are using a really small case with relatively poor air flow; think any intake that is reduced smaller than the face of the fan (side slots/etc) that there is a restriction on its own.

I would have yo agree with you on your premise after thinking on your build specs a bit, and taking into consideration of the 'full' value that may go through it. So my opinion is that It would indeed be better to direct exhaust all your radiator heat,   rather than heat the insides up partially negating  the cooling.

[Troika]

3 hours ago, Neo-revo said:

thats good,  and you do a thorough cleaning once a year is decent too,  when i discovered the 240, it was cause i was doing system maintenance, but with 2 year old fluid, (and only cause i wanted to mess with rad placement inside my case again)

 

If you are using a really small case with relatively poor air flow; think any intake that is reduced smaller than the face of the fan (side slots/etc) that there is a restriction on its own.

I would have yo agree with you on your premise after thinking on your build specs a bit, and taking into consideration of the 'full' value that may go through it. So my opinion is that It would indeed be better to direct exhaust all your radiator heat,   rather than heat the insides up partially negating  the cooling.

Yup, I've seen too many PCs come in for replacement parts because the static build up from dust killed them. Some people tell me that I clean my computer too often but I'd rather do frequent cleaning if it means I don't have to spend $120+ on replacing parts.

[SolarNova]

I speak from experence.

 

I use 3x 240mm Rads.

 

I have them all exhaust.

 

Why ?

 

Reciculation of warm air results in a reduciton in cooling.

 

My front rad is a 240 x 80mm Monsta Rad, in push/push. i originaly had it as intake, but it was effectivly a space heater, warming up the interior of my case dispite having the top 240 rad as exhaust and the rear rad also exhaust.

 

Problems will full negative pressure ?

Dust ..i have to clean my system much more frequently than normal as air is being pulled in from the side vent on the CM Storm Stryker case, and other smaller vents like those of the PCI-e blanking plates (which are vented).

 

i also tried a full positive pressure setup but that just made the inside of  the case really warm, which eventualy heated up the liquid in the Res, not to mention made SSD temps, VRM temps rise much higher than normal.

 

So if your using multiple rads, especialy enough to fill up the front and top of a case, i highly sugest running them as exhaust.

[Neo-revo]

9 hours ago, SolarNova said:

i highly sugest running them as exhaust.

Spoiler

i get those benefits by accident, but really it was cause i didn't want to keep hotswapping hdds in the 4 bay disc changer,  benifits gained were 6 hdd spots in quick install slides in dual 3x3 cages (i think i might be able to keep the top one and put a 480 in the base of my case again if i wanted.

 

@Troika When i ran both rads (420/480) in my main case i was careful to pipe it to the top rad first, (effectively negating the dangers as far as i convinced myself)  

Over time and further understanding of the thermodynamics involved, it was made clear to my understanding that the water didn't function like that, and if it did concerns would be had.   The idea that a closed loop in a computer operates like that.. i dont know why or how we all get this idea, perhaps it comes with our basic understanding of phase change systems mixed with over thought paranoia.

 

So i was messing with my peltiers the other time and seeing if i could make a heater that also made a fridge/chiller unit or some sort.

worked great. maybe too great. the hot side radiator with only a single plate got so hot i would need to build some sort of metal frame/support if i even thought about 'long' use

even then with it feeling hot to my touch (professional cook) so would burn 9 out of 10 people if they tried to touch it.   the in/out were basically the same temp and the entire rad all read basically the same where the fluid touched,   But it could jus tbe the lower flow high temp motors i was using...   But really the point was that the Delta C before/after  are usually quite close on water systems.    Only ones rated for high pressure (steaming)  like in a car get significant reading in the in/out.  But they also they have flow stoppers and an ECU to relay with that allows for extended cooling (staying in the rad longer)