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Need to bring temp delta down. Looking for advice. - Page 3

post #21 of 29
Quote:
Originally Posted by Buzz247 View Post

Good sir - not going to start a flame war here, but um.... you have it backwards. Positive pressure is far more likely to cause dust to settle in case due to air slowing since it can only move slowly out of cracks and holes as you said (Think about that for a sec you'll see what I mean I hope). Positive pressure only benefits cases with large venting i.e. HAF X etc. Solid panel cases benefit from negative pressure. Rad fans will only starve for air IF you have poor case flow design in the first place.... Air follows laws of fluid dynamics. need to read up a bit - if you'd like I can send you some research links on these topics that might help clear it up a bit.

Convection current are a law of thermodynamics. They effect every body of air calm or not. Yes, a fan will direct that flow, but point a fan down forcing air against normal path will not be as effective as blowing it up. I'm sorry but physics is physics all day long. Can this be done willy nilly any way you want? SURE!!! Is it the most effective? no... hence my statements. and oddly... again research articles back my statements.

no, if there is no airflow in a case, negative pressure, the dust will settle as it has nothing to keep it moving. how can any case benefit from negative pressure? the air is stale from not moving. it starves radiator fans.
air will go where a fan forces it. what do you think a ceiling fan does?
please read your own research and then research a little more.
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post #22 of 29
This is a matter of same words mean different concepts to user - negative pressure simply means more exhaust than intake from actual fan usage. Flow is still there - the usage i am referring to implies simply which direction the fans are pointed. In other words 3 70cfm fans, 2 out 1 in is negative pressure. your in fan actually produces more CFM in real testing due to increased negative pressure in an enclosed space. causes air to move more rapidly thru the case, rather than building pressure and causing dead zones and swirling as it would do in the same case with positive pressure. In a case with a lot of ports/venting, positive pressure allows air to pass thru more rapidly, whereas negative pressure causes deadzones due to air not being guided thru.

I read the research fine. Just seems a disconnect of concept.
Anyway, it is what it is. laws of physics do not change. so.... *shrug* believe what you will I guess. Not gonna argue proven fact.
post #23 of 29
i would love to see another thread dedicated to Positive VS Negative airflow. in my own experience, Positive airflow has always given me less dust inside, and cools the components better internally than negative.

as i said, i would love to know more about this matter. anyone care to start a new thread?
post #24 of 29
Thread Starter 
Wow, thanks to everybody, tons of great info.

Air flow is definitely not optimal. The room temp is usually between 65-70 °F. Case temp are usually around 80 °F.

Regarding my fan and radiator orientation, the fans in the bottom compartment of the case (down by the PSUs) are acting as both intake and exhaust so the air is passing straight through the bottom of the case (2 fans on window side are intake and 2 fans on opposite side are exhaust). I have 2 240 rads in the bottom. This seems like the best orientation to me because it gets the warm radiator air out of the case pretty quickly.

There are 3 120mm fans in the front of the case acting as intake. I currently have no radiator in the front.

I have a 480 radiator in the top of the case with 4 fans on it in a pull configuration (exhausting air out the top of the case).

Lastly, I have a 140mm fan on the back of the case acting as an intake. I'm using this as an intake not only to keep air moving around the VRMs but also to keep a slightly positive case pressure.

Quote:
Originally Posted by Buzz247 View Post

Good sir - not going to start a flame war here, but um.... you have it backwards. Positive pressure is far more likely to cause dust to settle in case due to air slowing since it can only move slowly out of cracks and holes as you said (Think about that for a sec you'll see what I mean I hope). Positive pressure only benefits cases with large venting i.e. HAF X etc. Solid panel cases benefit from negative pressure. Rad fans will only starve for air IF you have poor case flow design in the first place.... Air follows laws of fluid dynamics. need to read up a bit - if you'd like I can send you some research links on these topics that might help clear it up a bit.

Convection current are a law of thermodynamics. They effect every body of air calm or not. Yes, a fan will direct that flow, but point a fan down forcing air against normal path will not be as effective as blowing it up. I'm sorry but physics is physics all day long. Can this be done willy nilly any way you want? SURE!!! Is it the most effective? no... hence my statements. and oddly... again research articles back my statements.

I always though negative pressure would lead to greater dust buildup and poorer radiator performance for rad fans acting as exhaust. All my intake fans are filtered so if I have a positive pressure inside the case, air will flow outward through all the unfiltered vents and cracks in the case. A negative case pressure will create a vacuum effect of sorts and pull air through all the unfiltered vents and cracks.

This is just my understanding though. I'm not stubborn enough to think there aren't tons of people on this forum way more knowledgeable than I so I always keep an open mind. If you don't mind posting your sources I'd be very interested in reading them.

Also, while I would prefer to keep dust out of my case, if a negative pressure does in fact result in a noticeable cooling improvement, I definitely favor performance over the slight inconvenience of cleaning my case out every now and then.

Quote:
Originally Posted by azanimefan View Post

old time hand at water loops here... i'm going to have to chime in, in agreement with the guys saying you don't have enough radiator. I'd probably look to add another 360mm-480mm radiator in there somewhere.

I'd also look to swap out those noctuas with Scythe Gentle Typhoon AP-15s... Noctuas are awesome heatsink fans... and case fans... but as rad fans they tend to sport too little static pressure to be worthwhile.

Thanks for the suggestions azanimefan. I'll look into those fans. The reason I went with the NF-F12s was because they seemed to offer a nice compromise between noise and cooling performance (didn't hurt that I had a bunch of them lying around from a previous build either).

When I get some time I'm thinking about ordering a bunch of different fans and comparing them all in push, pull and push/pull at different fan speeds. I'm particularly interested in push/pull performance of different fans at lower fan speeds.

Also, I'm pretty sure you're correct that I'll need to add another 360 or 480. I'm gonna test out my system with the 140 and the 4 additional fans added to my 480 (for push/pull) before I decide though. I'm thinking I'll need to mod my case to fit anything larger than a 240 in the front (not a huge deal but would rather avoid if possible).


Thanks again for all the help.
post #25 of 29
  1. add some fans to the top so it's push pull , that'll get you 3 degrees of performance in a good scenario.
  2. add another 140mm radiator to the back and have the fan exahust out the case.
  3. add another 240mm radiator to the front and have the fans acting as intake. but make sure this 240mm is the LAST stage of the loop before entering the CPU/GPU, that way the air coming into the case will be the coolest.
  4. keep your bottom radiator setup.


that's what i would do.
post #26 of 29
Quote:
Originally Posted by ShoehornHands View Post

Wow, thanks to everybody, tons of great info.

Regarding my fan and radiator orientation, the fans in the bottom compartment of the case (down by the PSUs) are acting as both intake and exhaust so the air is passing straight through the bottom of the case (2 fans on window side are intake and 2 fans on opposite side are exhaust). I have 2 240 rads in the bottom. This seems like the best orientation to me because it gets the warm radiator air out of the case pretty quickly.

Can you modify this picture to show what you have going on in the bottom?

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post #27 of 29
he has a 900d. it has a 'basement'. air goes in the left side of the case through the rads and out the right side of the case.
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post #28 of 29
Quote:
Originally Posted by pc-illiterate View Post

he has a 900d. it has a 'basement'. air goes in the left side of the case through the rads and out the right side of the case.

the fans in the bottom compartment of the case (down by the PSUs) are acting as both intake and exhaust ?????
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post #29 of 29
Quote:
Originally Posted by billbartuska View Post

the fans in the bottom compartment of the case (down by the PSUs) are acting as both intake and exhaust ?????

it's a separate compartment. look at some video reviews on youtube on 900D. it's almost like its own separate compartment. so op has it setup so in that compartment, air comes in on one side and blows out on the other side, all happening in that compartment.
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