Best fan arrangement with a Noctua NH-D15 almost at a case exhaust hole?

[CRABBY GUY]

I have rethought my use of an AIO water cooler in my new build and have now chosen to use air cooling instead: a Noctua NH-D15 in a fairly small case, a Corsair 300R, to cool an Intel i7-9700K that will be overclocked. Yet I am confused about how the cooler's exhaust air should best exit the case.

Of the two 150mm fans that are part of the large NH-D15, the one that exhausts and sits right over the RAM will be very close to the two,140mm, side-by-side holes in the top of the case. With a third, nearly identical Noctua fan installed on the inside of the case, the photos I have seen show maybe three inches of distance between the outside of the case fan and the outside of the exhaust fan on the cooler. Thus, at most, there are four inches between the NH-D15 and the case exhaust hole.

Here are my questions:

1. In my office, with my computer cart, a straight-up exhaust would hit me right in the face(!). Would a 90-deg., 140mm inside-diameter fitting on the outside be helpful? Suggestions for a vendor? Would I be better off making something for this purpose? (Alas, few such skills here.)

2. Since there are two, side-by-side, 140mm holes in the top exhaust, would somehow blowing through both be superior, with or without a case fan or two? Again, suggestions how it might best be done and for a vendor?

3. The importance of a case fan here vs. a very short pipe or some other way of directing the air out of the case?

4. If a case fan (or two case fans, side-by-side) are used, how should their speed be determined, both for performance and noise?

 

[Darkbreeze]

No fitting. That would cause a further restriction and reduce cooling performance.

I would use the cooler as it was intended, OR move the front fan to the rear, but I would not do anything to affect the rear exhaust fan or any top exhaust fans.

If necessary, I'd turn the cart a bit so the exhaust isn't coming straight at you. If you increase the length of space the fan has to push air through to get it outside, you are creating a restriction and not only are you going to amplify the noise of the fan and fan bearing inside that wind tunnel, you're going to dramatically decrease it's ability to get heat out of the case with a minimum of restriction.

Would it work? Sure. Is it a good idea, not without a really, really good reason for having to do it and I can't think of one. Seriously, I'd point the case away from you before I'd even think of doing something like this.

As far as fan speeds go, the further along the chain, the faster you would want to fan to go so it does not create a restriction for the fans that come before it, and actually assist them overcoming any restrictions especially if they are not especially high static pressure models, but for any configuration really.

The rear exhaust does not need to be faster than the rear fan on the heatsink, so long as there is also a top rear fan in place as a second exhaust to help get all the expelled heat from the heatsink, out of the case.

 

[CRABBY GUY]

Does it matter if I mount the Noctua NH-D15 vertically or horizontally as regards noise and/or cooling? (Detailed info in first comment. Key: this is at the top of a Corsair 300R case. Heat would leave either through top or back of case.) I can measure temp and sound level if this is a major issue.

 

[Darkbreeze]

Tower coolers are only supposed to be mounted with the airflow running front to back through the heatsink. I realize there are some fools out there setting them up running bottom to top, but that is not an accepted orientation and is a poor idea ESPECIALLY if you have a high end GPU card that's putting off a good deal of heat, which of course will end up going straight through the heatsink.

Not a very efficient way to cool the CPU AND it completely borks up the airflow path that is supposed to be in use, with front intake flowing through and out the rear or top exhausts. Obviously, you CAN do this, but it's a bad idea and highly not recommended. With some coolers, it's probably not only a bad idea, but physically won't even work at all.

A lot of people have tested configurations including that sort of orientation and the results are typically extremely poor.

This is pretty much the way every cooling system aside from a few specialized water cooled configurations or very old top mounted PSU cases should be configured.