There are two general descriptions for air moving devices in electronic equipment. These can either be a type of fan or a centrifugal blower depending with their flow and pressure.
Fans generally deliver air in an overall direction that is parallel to the its blade axis. It can be designed to deliver high flow rate. A common example of a fan is a tubeaxial fan. It is typically used in chassis getting aerodynamic lift from the blade to move the air. Fans can work best against low pressure and can be available in sizes ranging from a 40 x 40 mm with a 10-mm thickness that can yield about 5 CFM (cubic feet per minute) and 0.11 inches of water to a 120 x 120 x 38 mm blowing upwards of 200 CFM. On another note, some 40 mm fans running at 13,000 RPM can also yield up to 24 CFM.
Blowers on another hand deliver air in a direction perpendicular to the blower axis at a relatively low flow rate. It can handle higher pressure and is available in sizes from the little 30 x 10-mm with 1.66 CFM and 0.370-in water devices to an amazing 159 x 40-mm with 61.8 CFM and 1.4 in water behemoths.
Chassis that has a lot of space vertically, such as 4U; and low airflow impedance with no filters and has multiple inlet/outlet openings, then a fan would definitely be a good choice – aside that it can move much more air. On the other hand, 1U chassis can use blowers. It may take up a lot of space but the height limitation of the equipment makes blower a better choice. While blowers will generate much higher static pressure compared to fans, it has the advantage of being quieter than multiple fans installed and is less expensive as well when it comes to cost.
Operational considerations for fans and blowers should also be considered when choosing an air-moving device for electronic equipment. One factor is determining the realistic specification for operating temperature rise. This is done by analyzing the temperature curves of fans and blowers, comparing them to achieve the one that will move the right amount of air to keep the chassis within the allowable temperature limits, as well as keeping noise levels at reasonable figures. Also, another factor to consider is the altitude, which for most designs, a factor of about 1.25 is used for altitude correction.
Some examples of blowers are Delta Electronics BFB0612H DC blower running at 3200 RPM providing 6.71 CFM with noise levels at just 34 dB. Another one is the BG0703-B042-000 from NMB Technologies that runs at 2,200 RPM with 7.40 CFM and noise level as low as 29.5 dB