What fan is slightly less powerful than delta?
I bought 2 of these very hyped Delta fans https://www.newegg.com/Product/Product.aspx?Item=N82E16835213001 to blow through my radiator but the fans are slightly too thick and I need 140mm fans. These fans are rated at 240CFM and the next best I can find is 80. Can anyone help me with some in between options? 150CFM without the fan being thicker would be great. probably less noise too.
Wow, don't use those. At all. Those are designed for cooling servers, notice the amperage. It pulls main power from the molex and uses the supplementary 3pin to adjust speeds. Both of which will not work right on cpu_fan header as that header requires a 4pin pwm fan. They only work on any of the sys_fan headers. They also don't work well on rads because of the huge motor housing, most of the airflow is only coming from the edges, so you miss most of the center cone, the middle of the radiator. Great for airflow at 4000-8000rpm, sound like a jet engine, but lousy for radiators.
Case Fan: Noctua - NF-A14 PWM 82.5 CFM 140mm Fan ($20.97 @ Newegg)
Case Fan: Phanteks - PH-F140XP_BK 85.2 CFM 140mm Fan ($17.88 @ OutletPC)
Case Fan: Corsair - ML140 Pro 97.0 CFM 140mm Fan ($27.93 @ OutletPC)
Case Fan: be quiet! - SilentWings 3 pwm 59.5 CFM 140mm Fan ($19.79 @ SuperBiiz)
If you are planning on using these fans on a radiator, there's a few factors that work in your favor, and some against.
A radiator works by warm liquids transferring heat to densely packed fins. These fins radiate heat, which is transferred to the air blown across the fin surface. Air in itself has its own thermal properties, which are far from perfect. It'll only absorb that heat at a specific rate, which isn't all that fast.
High pressure fans work best at lower cfm, you basically create a solid wall of air moving through the radiator. High cfm fans work best at higher cfm, blowing through the radiator picking up the heat and gone to be replaced with cooler air. But all that's up to a certain point. Too much air blowing through too fast doesn't have the time to absorb much of that radiated heat energy, increasing the cfm just makes it worse. With fans designed for too much pressure, the same applies, all that air is moving far too fast to do much good. So a balance needs to be struck, enough pressure to push the air past the fin obstruction at a decent rate, enough cfm to have the capability to absorb that much heat.
So it's not all in the numbers, far from it. Huge cfm on a radiator does nothing but create a whole bunch of noise, for little performance.
When reading the numbers, yes those Noctua fans will get high cfm. At high rpm. Anything less and the cfm drops.
I have a 280mm radiator. That's 2x 140mm fans, used in pull config. Generally rpm below @1200 shows better returns in pull, above 1500 shows better returns in push, and 1200-1500 makes no difference. My fans sit almost constantly 600-800rpm, with 800rpm when gaming pretty hard. Needless to say, it's almost dead silent. That's on Silent settings. To put it on max fan speeds of 1500rpm, even in push, only shows a 1°C drop at idle, and a 4°C drop at 100% cpu usage (i7 cpu). It goes from almost silent to noticeablely noisy for extremely little gains. Honestly not worth it.
If I used those 4k/6k/8k Delta fans, temps would probably be worse, simply because the air moving doesn't get saturated with radiated heat, and the motor housing is so huge that a good majority of the radiator surface will not see any airflow, the fan sits too close to the fin surface. Creates a huge 'donut'.
Those fans listed above, put out enough cfm to absorb the heat energy, with enough pressure to move that air adequately. Good balance without a ton of noise, or much of any noise really.
And no, size of the fan makes little difference to air pressure or cfm, that's entirely dependent on fan design and speeds of rotation. Entirely possible to get higher pressure from an 80mm fan than a 140mm if the 80mm is designed for pressure and the 140mm designed for cfm. Or the other way around. At equitable speeds, the 140mm will naturally be higher cfm, more blade surface, and with equitable design the 140mm will have higher pressure, more blade surface. Changing the design changes its characteristics in relation to a different fan.