Airflow

Hey guys,

I'm wondering if anybody could help me optimise the airflow in my new rig. I've made a diagram to show you its current layout :

[external image: Posted Image]

I had to swap the direction of the top fan when I realised that I had mounted the CPU heatsink and fan the wrong way round. I thought having two fans sucking air away from each other would create a vacuum. The CPU has a very good idle temperature and it doesn't really go much above 50 C when I'm running SETI@Home. (I thought that would be a nice way to test the PC). The GPU is around the mid 40's at idle and goes to about 65 C under load. The disk temperature is always very low.

I'm a bit concerned that the PSU is taking too much air from the GPU's intake. I know that two fans are feeding air in from the front, but a 40C idle temperature seems to be bit high when compared to the rest of temps. I do have an option to put in another 80CM fan directly above the GPU which could push in air and feed both the PSU and the GPU… but would that make any difference?

Is there any way that I could optimise the airflow to get the best possible temperatures all round? I suppose taking the heatsink off and reseating it to face the other way would make a bit of difference, but I think having two fans pushing air through the heatsink is probably a good thing. If I kept the top fan and the CPU heatsink/fan the same way, should I put some air filtering fabric between the top fan and the case to keep dust out?


Thanks in advance
Nahumi

Hi Nahumi. I generally make front fans and side fans intake, while all others are exhaust. This means you would swap the top fan around so it exhausts. Heat rises and an exhausting top fan is a good way to get rid of it. I'm not sure what you mean about your CPU fan? This must be an aftermarket fan, because stock fans have no "directional" properties. Your CPU fan, if directional should be blowing towards the rear exhaust fan. To cool your GPU you need to add the side fan so that it intakes (blows in) over the GPU. Don't worry about a dust filter. YOu have so many fans and holes in that case you'll never keep the dust out. I suggest not dropping any metalic objects through the top of your computer.

Thanks for the quick reply appleoddity, Yeah, I did think sticking a screw driver down the top might be a bad thing… You're right, the CPU heatsink is aftermarket. It's an Arctic Cooling 7 Pro. The fan is on the side as opposed to on the top of the heatsink and due to the way it's AMD conversion brackets were designed, it either pushes air up or down. When I mounted it I forgot to check which way the air would be flowing so it actually ended up trying to take air from the top. I swapped the top fan around and thought that the side fan would compensate. The case came with these two fans preinstalled and they both have speed toggles on them, both of which are set to medium. I'm going to increase the speed on the back fan to make sure that most of the air coming down from the top is still going out the back. I'll stick on an intake side fan like you suggested and report back with some new temperatures. I've also had a bit of a play around with nVidia's fan settings and was able to knock 9 degrees off the GPU temp, which is now idling at 34. The fan is obviously a bit louder, but I don't mind that if it keeps things a bit cooler. Thanks again, Nahumi

I thought it looked a bit like this case: http://www.newegg.com/Product/Product.aspx…N82E16811129058

I just bought this case a couple of weeks ago. I have it configured the way I described. Except I believe the side fan is 90mm.

My MSI Nvidia GTS250 is running at 39 degrees at idle - onboard fans at 35%. This is only 102 degrees farenheit. That doesn't seem excessive in the least. The whole computer is whisper quiet because all the fans are pretty much turned down all the way.

Yeah, I probably should have mentioned I had an Antec 300. I think the layout is roughly the same as the 900, but it looks less cool. So circa 40C is actually normal? I've had some issues with nVidia cards overheating in the past which has resulted in a fried 8600GT. Since then I have always been very cautious about temperatures. I've also been thinking about having a go at overclocking the CPU. When I bought it I was in two minds about getting the Phenom II 955 BE over the normal retail 940, but in the end I went for the 955. Should I make any special preparations in terms of airflow/cooling? And am I right in assuming that an increase in temp for the CPU would affect all other components? Or does it generally not make a difference? Sorry for all the questions. It's the first time I've built a PC from scratch and had to worry about how efficient the layout was. Thanks again.

Well, with your case, the top exhaust fan is very important. I would really try to get that switched back around so it is exhausting and adjust your CPU fan accordingly. Hot air rises, it is a large fan, and exhaust fans are more efficient that intake fans. It is probably the best fan in your system for running quietly, and keeping things cool by exhausting hot air. If you overclock your CPU you WILL generate more heat. It goes hand in hand. Overclocking is a very touchy procedure and requires a lot of patience and testing. On the same note, heat is always a problem in electronics. The cooler an item runs, the longer it will usually last. Thus, overclocking a CPU will reduce its life. Running a video card hotter than necessary will reduce its life. However, to address the 40C issue, in my opinion, this is perfectly normal. I like to convert things to farenheit so I have a real idea of how warm it is. This converts to 104 degrees farenheit. I take baths hotter than that. Its barely warmer than the human body. So, no, I don't think this is anything to be concerned about. On the other side of things, under full load I would try to keep a device below 70C, but in all actually I have monitored components in laptops that run at 80C or right in that area. Even that is only 176 degrees farenheit which should still be well within the limits of the chip. But, heat does reduce life span so you want to keep everything as cool as possible. It certainly doesn't hurt. However, if you keep things below 70C under full load, you are doing pretty darn good in my opinion. If one component runs hotter it is going to increase the amount of radiant and convection heat in the surrounding area or in the case overall. This will effect all other components in the case but there are so many variables to consider it would be hard to say how great the effect would be. In most cases, the effects would be negligible if you have adequate airflow. To sum things up, I see nothing to point a finger at in your original post about your temperatures.

Okay, thank you very much appleoddity. I'll refrain from overclocking anything until I can get my hands on some more TIM so that I can reseat the heatsink and get the air flowing in the right way. I haven't seen anything go above 50C (122 F) under full load, that's including the GPU. So I guess it'll be totally fine for a bit longer. Thanks again for the advice and clearing stuff up for me. Nahumi