Cooling a GPU from the side with 40mm fans (S4M)

tokumei

Minimal Tinkerer
Original poster
Jan 11, 2020
4
0
Hey all, I just recently completed my first build in my S4 mini. It works well and I love how tiny it is, but the one thing that bothers me is how loud the stock GPU cooler is. The particular card I have is an MSI RX 580 V1. I'm not sure whether this is normal for this model, but at idle there is a very noticeable hum from the stock fan, and so I'm looking for alternative ways to get air flow to the GPU.

With my previous graphics card I was able to use some 92mm fans with a sky bracket, but with this model the heatsink is so tall that they won't fit inside the case. I considered mounting them on the outside using some washers with the existing ventilation holes. This would work in theory, and it would be a nice unique touch, but I've got another idea - installing 40mm fans behind the front bezel and blowing air front-to-back.

This seems doable; I do have enough space to fit two or three 40x10s, the GPU fins are oriented horizontally, and it's possible to mod the front bezel to add some ventilation holes and mounting. My biggest concern is the thermals. I'm not an expert in this by any means, but from looking at the numbers in Noctua's listings, these fans have a significantly lower flow rate (NF-A9x14 : 50.5 m3/h, versus NF-A4x10: 8.9 m3/h). I'd also have to consider the impact of the fan's orientation - from the side the airflow will be mostly unimpeded, while from above the air is forced to make a 90-degree turn. I have no clue how much of a difference that makes. If there's anyone with more experience here, some insight would be greatly appreciated!
 

Kilrah

SFF Lingo Aficionado
Feb 20, 2017
128
112
Hard to say how loud your stock fan is, but multiple 40mm ones are almost certainly going to be louder and/or more annoying/whiny.
 

tokumei

Minimal Tinkerer
Original poster
Jan 11, 2020
4
0
Hard to say how loud your stock fan is, but multiple 40mm ones are almost certainly going to be louder and/or more annoying/whiny.
There are definitely loud and whiny ones, but that's not characteristic of all small fans. Noctua's NF-A4x10 is no louder than their NF-A9x14 at full speed.
 

tokumei

Minimal Tinkerer
Original poster
Jan 11, 2020
4
0
I did some of my own digging, and I found out that there is a straightforward relationship between air flow, heat transfer, and temperature difference:

CFM = 3.16 * Watts / DT (degrees Fahrenheit)

I couldn't find an official source for the TDP / heat dissipation of my graphics card, so I'm using the rated power consumption of 185W as an approximate (an overestimate?). If I want to maintain at most a temperature difference of 60C (110F), which would be a maximum temperature reading of 85C with ambient temperature at 25C or lower, then I would need airflow of at least 5.3 cfm (9.0 m3/h). With two or three fans, and each fan rated at 8.9 m3/h, that leaves quite a bit of headroom for inefficiencies (resistance, air bypassing the heatsink, etc).
 
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Kilrah

SFF Lingo Aficionado
Feb 20, 2017
128
112
There are definitely loud and whiny ones, but that's not characteristic of all small fans. Noctua's NF-A4x10 is no louder than their NF-A9x14 at full speed.
In my build I have 3x NF-A9x14 plus the GPU fan, and an NF-A4x20 in the PSU. When under full load the system fans make the most noise indeed but it's soft noise that's not disturbing, and what you hear most over all of them is the whine from the little one.
 

tokumei

Minimal Tinkerer
Original poster
Jan 11, 2020
4
0
I appreciate your concern, but really, that's not what I'm worried about. I just want a good cooling solution that fits within my physical constraints, is quiet / near silent at idle and low loads, and is tolerable at full load. I'm not concerned about mid/high frequency whining as long as it is moderately quiet, as I mostly wear headphones while the computer is in use at that kind of utilization.

With my current idea, I highly doubt it's going to be any louder (and expect it to be much quieter) than what I currently have. I just need to figure out whether it will provide sufficient cooling.