Understanding the actual static pressure of fans in real-world conditions.
Understanding the actual static pressure of fans in real-world conditions.
Hello everyone,
Thank you in advance for your assistance.
I've been researching case fans for some time now, but I still struggle to grasp the optimal static pressure for different situations. While I understand that 4 to 10 mmH₂O is considered high and anything below one isn't ideal for a radiator, it doesn’t fully clarify how these systems operate. This leads me to ask: in real conditions, what pressure does a fan encounter when operating through an open mesh with a dust filter, or near a radiator or air cooler of varying thickness? What factors contribute to resistance, and how can we estimate the value in mmH₂O?
I’d like to understand based on estimates whether using a fan with 170m³/h and 5mmH₂O in a mesh front plus dust filter setup would move more or less air compared to another fan. Specifically, if one fan has 2.5mmH₂O instead of the usual value and receives 30 m²/h, what would be the difference?
This question is among the most insightful I’ve encountered. It suggests that assuming a nearly linear relationship between resistance and airflow is reasonable, so knowing resistance in certain scenarios could provide a solid estimate. Someone could share a method for calculating such resistance or clarify what 1mmH₂O represents in pressure terms?
I appreciate your time, effort, and expertise.
What you're really looking for is a P&Q chart. The "static" in static pressure means no air is moving. This makes it useless for cooling. The P&Q chart gives a curve of air flow at various resistances (pressure drop). Airflow is generally non linear. Add in a variable like fan RPM which tends to be goemetric in it's effect and things get complex in a hurry.
Here's a spec. sheet from a Delta 120x38mm 12V. fan.
http://www.delta-fan.com/Download/Spec/A...H-SP00.pdf
Here are some fans at Digi Key filtered the same. Pages of them You can see the spec. sheet for each one.
https://www.digikey.com/products/en/fans...&pageSize=
Add in...
My response is likely to fall short of your technical interests (which is commendable). I simply bypass the promotional fluff and opt for industrial cooling fans that Dell and HP employ. Usually, a fan with greater thickness provides better airflow and pressure compared to a thinner one. I also consider the amperage rating, thinking that higher equals better.
I tend to choose options like 120x38mm rather than the 120x25mm aftermarket versions, opting for models rated at .8Amp or more instead of the lower .3Amp ones. Brands such as Delta, Sunon, MBT, Nidec, AVC, and Foxcon are popular choices.
My top pick is the Delta AFC1512DG 150x50mm with a 1.8A rating from certain Dell dual CPU workstations. It's a 6"x2" model.
it'll be much simpler to simulate using CAD tools; what you're sharing requires accurate measurement devices, inputting the details to calculate, the outcome would be impressive. some advanced vendor could benefit from this, and in the end, this effort will lead to a more efficient blade design. noctua has already achieved it and named it an anti-stall knob. for those who won't test it, any useful data is valuable.
Here’s a revised version of your text:
Thank you for your responses! I reviewed several industrial and heavy-duty fans, but didn’t obtain much useful information from them.
To find more reliable comparative data, I discovered this link:
https://us.hardware.info/category/23/cas...estresults
The main point is that the information provided by manufacturers seems largely unreliable—especially the database entries (this is clear when comparing enermax’s T.B.Silence PWM 140mm, which claims to be a 9db fan but delivers results above 44db). This suggests a consistent problem with enermax.
I also noticed similar concerns about performance drops in fans tested on radiators, with no clear correlation and some 10mmH20 models showing higher losses than 0.5mmH20 fans. After further analysis, it seems measuring conditions is subjective and only meaningful within the same manufacturer (at most).
The link above has become a bit of my primary source of trust, as I’ve confirmed several data points and relationships between tests, even with small sample sizes.
This doesn’t mean I’ve given up on the mathematical side of things.
I came across another resource:
https://www.captiveaire.com/manuals/airs...taticPress
While I’m not ready to apply it or draw strong conclusions just yet, it might be useful for others (just out of curiosity).
It’s still disappointing that the high RPM variants are no longer available, especially since my testing and calculations showed this fan performed exceptionally well.
can't completely escape sound pressure level problems, as it depends on how well the PC enclosure reduces internal noise.
Some reviewers, like xtremerigs.net, have tested many rads; readers such as me focus only on the data before choosing the best cheap rad for my build. I think this forum's members also prefer certain rads that help keep their builds cool.
Hardware Labs launched the "optiFlow" push-pull rad, which aims to boost air pressure on the radiator core and fix static pressure drops. The push fan creates higher pressure near the pull fan, while the pull fan generates higher pressure close to the push fan.
What you're really looking for is a P&Q chart. The "static" in static pressure means no air is moving. This makes it useless for cooling. The P&Q chart gives a curve of air flow at various resistances (pressure drop). Airflow is generally non linear. Add in a variable like fan RPM which tends to be goemetric in it's effect and things get complex in a hurry.
Here's a spec. sheet from a Delta 120x38mm 12V. fan.
http://www.delta-fan.com/Download/Spec/A...H-SP00.pdf
Here are some fans at Digi Key filtered the same. Pages of them You can see the spec. sheet for each one.
https://www.digikey.com/products/en/fans...&pageSize=
Add in other manufacturers and other sizes and you have thousands of options.
The P&Q chart reviewed at the provided link represented a major part of the larger "PC cooling" trend. It offered a focus on optimizing fans and cases for better balance between cooling efficiency and noise levels. Achieving a 1 to 5 degree Celsius difference from ambient temperature was considered significant.
Previously, I prioritized fan shroud design over fan selection and case setup simply to gain a few degrees of cooler performance. After switching to a tempered glass case, I abandoned that approach and now use a push static pressure fan, followed by a radiator fan, which provides better results.
William P would likely find the technical details you mention interesting. He tends to avoid unnecessary advertising fluff and prefers reliable industrial cooling solutions such as those from Dell and HP. He believes that a fan with a higher thickness generally provides better airflow and pressure compared to a thinner one. He also considers the amperage rating, thinking that more is better.
He tends to choose models like the 120x38mm instead of the smaller 120x25mm variants, opting for higher ratings such as .8Amp or above rather than the lower .3Amp "toy" options. He looks at brands including Delta, Sunon, MBT, Nidec, AVC, and Foxcon.
He specifically mentions the 120x38mm model from Dell dual CPU workstations, noting it’s a 6"x2" fan.
From what he read on Noctua’s buyer guide, there seems to be minimal variation in performance between their static pressure and airflow fans—his impression is they deliver similar results. He appreciates the point about the Dell 120x38 model and suggests that larger sizes would be better for whole-house cooling.