Radiator thickness for quiet pull fan - 45mm or 60mm?

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KrzysiekX10

KrzysiekX10

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Apr 6, 2014
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One of the radiators I'd like to have in my new liquid cooling loop is going to be either 45mm or 60mm thick (both are Alphacool 140mm 9FPI). The fan configuration on it is going to be one fan in pull.
The maximum RPM the fan is going to reach is 1500 (with the static pressure of 1,98 mm H2O), but most often it is probably going to operate at about 1100 RPM (with 1,41 mm H2O).
So which radiator is going to be better? Is the 60mm one going to win according to the "the thickier, the better" rule or is it going to perform worse because of the fan's low speed?
 
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KrzysiekX10
O wow...
I've just checked a site, on which somebody used really serious, professional gear to test performance of two radiators. Both of them were 120.3 and 11 FPI. One of them was 47mm thick, the other one 60mm. I've checked their performance with three 1000 RPM fans in pull and water flow 1,5 GPM.
Guess what?
The 47mm radiator was performing a little bit BETTER.

So...
I still think I should get the 60mm thick radiator, since the difference, as I mentioned, was very small, the FPI was a bit higher than mine is going to be and apart from that, the 60mm thick radiator is going to get bigger performance boost after speeding the fan up.

Well, I answered my question myself. Anyways, thank you for your pieces of advice.
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SproutyPC

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A thicker Radiator is typically a much better choice than thinner, more surface area allows for the heat to transfer to the fins and with a typical decent set of fans (decent, not top end) you will still yield wonderful results.
 
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KrzysiekX10

KrzysiekX10

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Apr 6, 2014
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O wow...
I've just checked a site, on which somebody used really serious, professional gear to test performance of two radiators. Both of them were 120.3 and 11 FPI. One of them was 47mm thick, the other one 60mm. I've checked their performance with three 1000 RPM fans in pull and water flow 1,5 GPM.
Guess what?
The 47mm radiator was performing a little bit BETTER.

So...
I still think I should get the 60mm thick radiator, since the difference, as I mentioned, was very small, the FPI was a bit higher than mine is going to be and apart from that, the 60mm thick radiator is going to get bigger performance boost after speeding the fan up.

Well, I answered my question myself. Anyways, thank you for your pieces of advice.
 
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lwcdnet

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Mar 8, 2014
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Your logic seems correct according to everything I've read so far about 45mm vs 60mm thick radiators - Slightly less cooling on the 60mm when the fans are going slower, but more cooling capability on the 60mm's at higher fan speeds.

It seems that each user will then need to make up their mind about whether they care about noise, and if they do, they'll be wanting to run their fans at lower speeds, making the 45mm radiators more attractive to that user group.

For me, I'm opting for going the 60mm route (alphacool too). Can always runs slow/quiet, with SLIGHTLY less cooling, but always have the option of cranking the fans if trying to eek additional cooling out of them. From what i've seen on reviews (youtube - Linus and JayZ), This is moreso important for the CPU cooling than it is for GPU cooling. I saw some reviews where it was noted that additional cooling of the GPU doesn't always buy you more overclocking headroom, but certainly it is ALWAYS better to have your components cooler.
 
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Karadjgne

Karadjgne

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Pull orientation on a radiator typically results in better performance at below @1200 rpm, push I'd better at 1700+ and it's about equal at 1300-1600. Pull is almost a passive system as there is no 'breeze' like a more active 'push' system, and totally relies on the amount of air being able to be drawn by the fan. All things being equal, what goes out, must come in, so a higher cfm fan, with a decent amount of sp is king, as it will draw the most amount of air through the radiator. As to thickness, that's on a bell curve. A medium rad @47mm will have the best results, thick enough to present a decent amount of area, thin enough not to create too much of an obstruction preventing draw. The thin 30mm rads don't have the area to be that effective, and the 60mm rads are too thick to allow decent airflow.

Of course all this is subjective. A lot will depend not only on fpi but also on fan design. Directed airflow designs like the NF-F12, work better in 'push' no matter what rpm, and some well balanced fans like the scythe GT work the same push or pull.

Testing is a good thing, but can be somewhat biased unless the full range of options in rad/fan designs is taken into consideration
 
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lwcdnet

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Thanks Karadjgne - There are so many variables that it's difficult to know when test results from people are even valid. Take thermal paste for instance - A good Watercooling system being tested with inferior thermal paste will yield "less-than-deserved" results. Another factor is the "CPU lottery" (Or whatever it's called that refers to the variability in what you get for the same model CPU (in it's ability to overclock, etc.)). If people are measuring the CPU overclocking results from different watercoolers to determine what watercooler is the best, then all sorts of factors come into play, like the CPU lottery itself, the Thermal Paste being used, whether the ambient room temperature was the same during all tests, and so on....

But there ARE people out there that try to remove as many variables as possible in their tests, and when you see enough test results showing similar results, then you have some justified credibility in the results.

You seem to be saying 47mm is a sweet spot for radiator thickness. I don't disagree, for many it will be. But for those who have no problem with higher fan noise and want the best watercooling results possible, I think going the 60mm thickness is the way to go. Do you agree?
 
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Karadjgne

Karadjgne

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I'm on a phone, so sometimes autocorrect gets the jump on me, but for a pull setup with an average fan at low rpm, then yes the 45mm rad will show better results on average. However, most cpu fan curve setpoint state at 70% duty cycle, the fan will be at max, or roughly @70°C for Intel. If you have a 1500 rpm fan, even in pull, you'll get better results from a 60mm at that speed, being @ the same as push. The only time the 45mm rad outperform in efficiency is if you keep the rpm lower, say below 900 rpm max speed, by either LNR or software. This is best accomplished by overcooling, using a cooler well beyond the heat levels of the cpu. It's playing with fire to take an h-60 on an i7 4690k OC, and limit it's cooling potential with low fan speeds, for example. Easily done by an h-80i or bigger cooler.

Noise is personal. If it doesn't bother you, then use the rad in push, set your fan curves higher, 900rpm at idle, 1500 at 55°C and you'll get max performance on a 60mm every time vrs a 45mm.
 
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