Panaflo U1 Ultra High Performance 40mm Fan - Sleeved
The secret behind the low sound and high CFM of the Panaflo fan is the use of Panasonic's Hyperflow Technology. Essentially this means that it uses a sleeve setup yet still has all the benefits and longevity of ball bearing technology.
Panasonic's Hyperflow Technology:
"Panaflo's unique hydrowave bearing (HWB) addresses the traditional weakness of sleeve bearings axial friction. By utilizing our unique HWB system, the thrust plate "floats" on a circulating film of oil, which greatly reduces the axial friction and the bearing's deterioration. The HWB pattern on the bearing virtually eliminates thrust plate contact which is depicted above.
As the shaft rotates it acts as a pump constantly circulating the oil in the radial, as well as the axial direction. The sealed system and reservoirs of oil maintain the proper lubrication to minimize mechanical contact and prolong the fan's life expectancy. The radial direction analysis shown above is essentially the same as a traditional sleeve bearing. Panasonic's unique HWB reduces the axial contact."
According to Techwatch, "the low sound and high cfm is all due to their "hyperflow" technology. It basically means that it uses a sleeve setup (versus the ball bearing etc) but still retains the benefits of the ball bearing method....All it really means in layman's terms is that the fan is more efficient and will last longer.."
Techwatch go on to compare the Panaflos to other fans such as the common Sunon equivalent: "Of course, the noise levels aren't the only factor, things such as the pitch of the sound. The Delta and the 120mm Sunon are by far the biggest noise makers, and it certainly can become irritating if you sit at your PC for extended periods."
For a more details check out the TechWatch review.