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Reversing Airflow From Normal
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18. October 2009 @ 16:38 |
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My current build uses a GB P55-UD5 mobo and I had so much luck installing an Arctic Cooler Freezer 7 Pro in my last build (on an Intel DP45SG board) that I automatically bought one of their new Rev. 2s for this one. Alas and alack, the tall Corsair DDR3 sticks are too close to the processor for the cooler fan.
I am considering committing the Cardinal Sin of blowing the hot air from my CPU cooler back into my cabinet--over the memory sticks.
My cabinet is a mid-tower CM-690 with the usual exhaust fan at the top rear of the cabinet (see here). I plan to turn this around to be an inlet fan, add two inlet fans in the side door and place two exhaust fans in the top of the cabinet. I found with my previous build that in spite of the two fans blowing toward the rear vent, most of the heat was pulled out by a top exhaust fan.
The memory sticks are Corsair Dominator style with the big heat sinks. Will the increased air flow over them, albeit warm air, hurt or help them or will they really notice?
The processor is an i7-860.
Should I just give in and buy a different CPU cooler or will this change in air flow be acceptable?
Dick
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18. October 2009 @ 17:22 |
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Quote:
I am considering committing the Cardinal Sin of blowing the hot air from my CPU cooler back into my cabinet--over the memory sticks.
Don't, as other than making your CPU run hotter (in addition to everything else) it completely negates the point of having nice heatspreaders on the memory in the first place.
Either get a different CPU cooler that will fit, or just use the RAM in slots 2 & 4 instead of 1 & 3 (This was my approach).
Quite frankly, you should be using something a bit more powerful than a Freezer 7 with an i7 860 anyway.
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18. October 2009 @ 18:34 |
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Originally posted by sammorris:
Quite frankly, you should be using something a bit more powerful than a Freezer 7 with an i7 860 anyway.
What would you recommend?
Dick
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18. October 2009 @ 18:40 |
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18. October 2009 @ 19:11 |
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Is the Ultra-120 cooler tall enough to clear the top of heatsinked memory sticks with a 25mm thick fan attached or is it still necessary to keep the first memory row empty?
Dick
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18. October 2009 @ 19:13 |
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18. October 2009 @ 21:05 |
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If the HSF were closer to the memory slots, would a heat-sinked stick in the first slot fit under the fan and fins?
Dick
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18. October 2009 @ 21:08 |
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Low profile memory possibly would, but dominator memory would not.
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18. October 2009 @ 21:21 |
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Lots to think about, but I think I am going to give this reversed airflow a chance.
One thing in my favor is that the design of the CM-690 case allows me to mount two 120mm exhaust fans immediately above the mobo. With two more side mounted inlet fans above the board, another pulling air in from the bottom/front and the reversed "exhaust" fan, I think I will be able to create enough positive pressure for an adequate flow across the mobo.
Needless to say, I will be keeping a very close eye on all temps as I bring the new build up.
Thanks for all the ideas.
Dick
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18. October 2009 @ 23:12 |
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Originally posted by k7vc:
Lots to think about, but I think I am going to give this reversed airflow a chance.
One thing in my favor is that the design of the CM-690 case allows me to mount two 120mm exhaust fans immediately above the mobo. With two more side mounted inlet fans above the board, another pulling air in from the bottom/front and the reversed "exhaust" fan, I think I will be able to create enough positive pressure for an adequate flow across the mobo.
Needless to say, I will be keeping a very close eye on all temps as I bring the new build up.
Thanks for all the ideas.
Dick
You might be able to copy what the OEMs would do...get some cardboard or thin plastic sheets and make a duct to take the hot air strait to a vent.
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19. October 2009 @ 00:39 |
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Originally posted by KillerBug:
You might be able to copy what the OEMs would do...get some cardboard or thin plastic sheets and make a duct to take the hot air strait to a vent.
I don't think I'll need to, Killer. Picture your typical mobo in a tower case with a bottom-mount PSU. The mobo is mounted at the top of the case. The top third of the board contain some of the worst offenders in the heat category--processor with its HSF and memory. This heat will naturally rise to the top of the case. In my case, the top of the board is within a few cm of the top of the case and the top of the case is stuffed with two 120mm exhaust fans. The heat from these two particular sources really has nowhere to go but out.
I have two double graphic cards which in theory will vent most of their own heat out their own rear vents. (I love theories; they make engineers smile and technicians cuss.)
Just like my first build (the "BOINC Blaster"), this is a learning experiment for me. I don't have room for an ULTRA-120, so if this doesn't work it will be time for me to get creative. :)
Dick
This message has been edited since posting. Last time this message was edited on 19. October 2009 @ 00:49
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19. October 2009 @ 07:09 |
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I'm pretty certain you do have room for an Ultra 120 in there. Of course, whether you can afford one is another matter.
Ultimately, there's no reason why reversing the CPU cooler wouldn't work, but you are going to be running your CPU and RAM quite hot. Slot vented graphics cards don't vent all their heat out the back either, so the CPU and memory are seeing some of that heat too.
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19. October 2009 @ 13:31 |
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Originally posted by sammorris:
I'm pretty certain you do have room for an Ultra 120 in there.
I would have room for a 160mm cooler if it wasn't for my second side intake fan being directly over the top of the processor. With that side fan in place I'm limited to something in the Ultra 90 category. Then again, reviews of the Ultra 90 with a decent 90mm fan put it a close 2nd to the Ultra 120.
But I still have options: if I think an Ultra-120 would buy me more systematic benefit than the side intake fan, I could try that configuration. Then again, replacing my side, front and top fans with something more efficient than the standard silent Cool Masters would definitely move more air into and out of the case.
Originally posted by sammorris:
Ultimately, there's no reason why reversing the CPU cooler wouldn't work, but you are going to be running your CPU and RAM quite hot.
Keep in mind I'm not reversing the CPU cooler, I'm reversing the top side exhaust fan. The CPU cooler assembly itself is simply being turned around so that instead of blowing warm air from the memory slots across the cooling fins and toward the exhaust fan, I'm blowing cool(er) air from the now intake fan across the fins with the resulting warm(er) air blowing across the memory. This would bother me a great deal more if I wasn't pulling all of that warm post-HSF air directly out through the case-top exhaust fans.
I did some experimentation with my previous build. I had room for a Freezer 7 and had it pointed directly toward the rear exhaust fan. I also had a case-top exhaust fan sitting directly between them. 99.9% of all the heat from the Freezer 7 was pulled out by the case-top exhaust fan. The rear exhaust fan could have just as well not even been there.
Originally posted by sammorris:
Slot vented graphics cards don't vent all their heat out the back either, so the CPU and memory are seeing some of that heat too.
Absolutely. That's why I'll be running some temperature studies to see how effective my two lower intake fans are at pushing the heat from the graphics cards up to the case-top exhaust fans. (The internal Corsair PSU fan will take care of itself.)
There are times things are done the way they are because time and time again that way has been proven to be the best. There are other times it's just because that's the way they've always been done. Trying to prove or disprove one or the other is a great way to learn, regardless of the outcome.
Dick
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19. October 2009 @ 14:11 |
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I do remember coolermaster cases being needlessly narrow, but it hadn't occurred to me that the problem with the RC-690 is having a top side fan and not the extra width required to fit one, another bright idea from coolermaster... o_o
The Ultima-90 and Ultra-120 aren't widely far apart for cooling but to get the same performance as an Ultra-120 with an ultra-silent (800rpm or so) 120mm fan fitted, you need the Ultima-90 to have a super-high (3500rpm+) fan fitted, which will make your ears bleed.
Apologies if I misunderstoof your plan, the way you worded the post at the start (and indeed your last post as well) suggests you were going to turn the CPU cooler around. What you are doing with using a pair of top fans opposite ways round (one in, one out) is creating a cyclic cooling system. This allows the cooling of an area of a case without getting much of the air required into any other parts of the case, and is most commonly used for cooling hard drives at the front of the PC. The reason why it isn't used for anything more powerful is because it is very inefficient - half the air that goes in is the hot air that just came out. When there is plenty of air around (i.e. the PC isn't trapped in a corner) and powerful fans are used, brute force airflow can ensure that it's not just the hot air that comes back in. Ultimately though, in this example you'd probably be better off just not having the second fan there at all. Remember, heat rises, so even with no fan there, the combined force of the other fan, the intake fans in your case, and the laws of heat rising, you effectively have a weak fan there already even if the slot is left open.
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19. October 2009 @ 14:57 |
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Originally posted by sammorris:
I do remember coolermaster cases being needlessly narrow, but it hadn't occurred to me that the problem with the RC-690 is having a top side fan and not the extra width required to fit one, another bright idea from coolermaster... o_o
The CM case is roughly 177mm wide. The side panel was designed to be a outlet vent for the standard Intel-style cooling fans. Optionally you can put a fan--either intake or exhaust--in its place. See the photo here.
Originally posted by sammorris:
Apologies if I misunderstood your plan...
Communications is a two-way street and the fault could just as easily be mine.
All non-radiant cooling systems are cyclic to some degree. You have cooler outside air being pumped into a case so that hot air inside the case can be pulled along as both exit as warm air.
By reversing my CPU cooler I intend to turn the entire HSF around 180 degrees so the fan continues to blow into the HS, but the exiting warm air is aimed back into the case instead of toward an exhaust port or fan. The exhaust fan on the back of the case IS being reversed and turned into an induct fan to feed cool air from left-to-right to the HSF.
The key to this working is that the exhaust fans along the top of the case will pull out the resulting outflow from the HSF before it has a chance to significantly increase the heat of the memory and other surrounding components.
The primary purpose of the lower intake fans is to help the naturally rising heat currents pull the heat up away from the cards and flow toward and into the case-top exhaust fans.
I agree that the top fan mounts would function nicely as passive heat vents even without any fans, but I have determined that having fans up there significantly increases the outflow of heated air.
I seem to remember one lesson in first-year thermodynamics where a hot air exhaust vent was placed directly below the cool air intake vent. The thing practically started feeding on itself. :)
Dick
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19. October 2009 @ 19:03 |
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This is what makes the RC-690 an odd design. Top fans are typically used as exhaust, but side fans are typically intake, so top side fans are rare.
The comment about all systems being cyclic to an extent is true - but it is greatly exacerbates by the fans being next to each other. In general it's not a practice I've found beneficial, even for cooling a hard drive, let alone a CPU.
So my original comment was right, you are turning the CPU cooler around. Again, this isn't something I recommend, as it is not just the CPU and RAM heat you have to consider, but also that of the voltage regulators on the motherboard, and the chipset. All of this is being forced in the wrong direction, and the only way this will not have a severe impact on temperatures is if the RAM is actively cooled (such as with the dominator fan module) and the top case fans are very aggressive. Ultimately, it's more efficient to do it the normal way round. I don't really see why it's being done this way, but if you are completely reversing the airflow pattern you ought to make it complete by swapping the rear exhaust fan to intake as well.
The CPU will not heat the RAM up in a normal situation, as the CPU pulls the air from the RAM away into the rear of the case. In this way, the RAM is being heated up by the CPU, which is detrimental as CPU cooling systems are far more powerful.
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