The fan that is marginally less powerful than Delta.
The fan that is marginally less powerful than Delta.
I purchased two of these highly advertised Delta fans to cool my radiator, but they are a bit too bulky and I require fans with 140mm diameter. They have a rating of 240 CFM, while the closest alternatives I found are around 80 CFM. Would anyone could suggest some options in between? A 150 CFM model without increased thickness would be ideal, possibly quieter as well.
When considering these fans for a radiator, several elements support your choice while others present challenges. A radiator functions by transferring warmth from hot liquids to densely arranged fins, which then emit heat into the surrounding air. The air itself possesses varying thermal characteristics, absorbing heat at a limited pace, which isn't ideal.
High-pressure fans perform optimally at reduced cfm, forming a dense airflow through the unit. Conversely, high cfm fans are more effective at higher flow rates, drawing in heat and expelling it, but only up to a certain threshold. Excessive air movement can hinder performance.
These parts are built for cooling servers, and the amperage is noticeable. They draw main power from the molex and use a third pin to fine-tune speeds. This setup won't function properly with the cpu_fan header since that requires a four-pin PWM fan. It only works with any of the sys_fan headers. Performance drops significantly on radiators due to the large motor casing, limiting airflow mainly to the edges rather than the center cone, which is the main area for cooling. Ideal for high RPM ranges (4000-8000rpm), producing a jet-like sound, but not effective for radiator cooling.
If you intend to employ these fans with a radiator, several elements favor you while others work against you.
A radiator operates by transferring warmth from hot liquids to a network of closely packed fins. These fins then emit heat, which is carried away by air flowing over their surface. Air possesses its own thermal characteristics, which are not ideal. It can only absorb the heat at a certain speed, which isn’t very rapid.
High-pressure fans perform optimally at lower cfm, forming a dense layer of air that moves steadily through the radiator. Fans with higher cfm are more effective at higher cfm, drawing in heat and expelling it as cooler air. But there’s a limit. Excessive airflow at too high a speed doesn’t absorb much heat efficiently, and increasing cfm further only exacerbates the issue. Fans built for excessive pressure behave similarly—moving air too quickly to be effective. A proper compromise is essential: sufficient pressure to push air past the fin obstruction at a reasonable rate, combined with enough cfm to handle the heat load.
This isn’t just about numbers. Large cfm on a radiator mainly results in increased noise without significant performance gains.
When examining specifications, Noctua fans typically deliver high cfm at high RPMs. Lower speeds cause a drop in cfm.
Perspective:
I own a 280mm radiator—two 140mm fans, used in a pull setup. Generally, speeds below 1200 RPM yield better results in pull mode, above 1500 RPM improve push performance, and between 1200–1500 RPM offers no significant difference. My fans run nearly continuously at 600–800 RPM, with a peak of about 800 RPM during intense gaming. It’s almost silent on Silent settings. Setting the fan to its maximum speed (1500 RPM) in push mode only reduces temperature by around 1°C at idle and 4°C under full CPU load (i7). The difference becomes barely noticeable for such a small gain. Honestly, it’s not worth the effort.
If I used the 4k/6k/8k Delta fans, temperatures would likely rise even more, since the airflow doesn’t fully absorb the radiated heat, and the motor housing is so large that most of the radiator surface remains stagnant—creating a significant 'donut' effect.
The fans I mentioned above provide enough cfm to manage heat effectively, with sufficient pressure for adequate air movement. This offers a good balance between performance and quiet operation.
Size alone doesn’t determine air pressure or cfm; it depends on fan design and rotational speed. It’s entirely possible to achieve higher pressure with an 80mm fan than a 140mm one if the latter is optimized for pressure and vice versa. At equal speeds, the 140mm tends to offer higher cfm, more blade area, and better pressure, while the 80mm may excel in another aspect. The characteristics shift depending on the fan’s specific engineering.
Noctua produces a number of top-notch PC fans, many of which are among the quietest available.