Centrifugal Blowers

Centrifugal blowers are often the most common type of fan. This article will cover why they are so popular and what makes them so different from other types of fans.

------------------------------------

What is a Centrifugal Blower? ------------

Blowers are a type of fan that use an impeller or propeller to “lift” air into the machine, using centrifugal force to push it out. They have three main components: an intake grille or blade; an impeller; and a casing with matching grille on the outside that helps to direct air flow where desired.

The main difference between blowers and other types of fans is that a blower's impeller is shaped like a disc or circle. This allows it to spin at high speeds, forcing air from the center of the impeller outward. The direction of air flow is determined by the direction in which the impeller blades are spinning.

Consequently, centrifugal blowers are most commonly used to move air outwards from a central point, whether because of inside or outside airflow needs or to create a stream of air. [The article points out that many fans are powered by a fan motor, while blowers are powered by a propeller. The writer goes on to say that this difference is the most significant.]

How Centrifugal Blowers Work ------------

The basic function of a centrifugal blower is to force air outwards from the center using centrifugal force. This type of motion accelerates air particles and forces them to leave their original position. As the particles move outward, they tend to follow the path of least resistance, which is away from the center where they were formed. The end result is that more and more air leaves the region closer to the center as air flows outward from there, allowing cold air to rise. [This is a very simplistic explanation of the process. The Wikipedia article on blowers offers a much more detailed description, if you are interested.]

Popular in Cooling Systems -------------------------

This type of blower is most commonly used in air conditioning and refrigeration systems. Since this is one of the oldest technologies for cooling, it's also among the most developed.

The first centrifugal blowers were developed in the 19th century, and they've remained popular ever since. They are commonly used as part of commercial refrigeration systems, but they are also used to cool houses along with other types of equipment that requires chillers or compressors to operate.

Blowers used in refrigeration systems tend to be low-pressure blowers, which are able to move air at lower speeds than high-pressure blowers. Since refrigeration systems use compressors that can generate a lot of force, it's necessary to have a blower that can handle the pressure and force coming from the compressor. High-pressure centrifugal blowers are most often used as part of industrial applications or large commercial cooling systems.

High-pressure blowers tend to be more durable, since they need to operate under a lot of stress in order to keep up with the work load. They are often run very slowly, which allows them to partially overcome the negative effects of corrosion and other wear on their moving parts. [The article also says that centrifugal blowers are quite inexpensive compared to other types of fans. This same can be said for low-speed blowers.]

Speed is Key ---------------------------

Speed is the most important factor when it comes to choosing the right fan for any application or system. High-pressure blowers with very high speeds can generate a lot of air movement, but they also tend to run much slower than low-pressure models. This means that their impeller blades don't need to spin nearly as fast, allowing them to be more easily manufactured while still remaining effective and efficient.

Centrifugal blowers are available in a wide variety of speeds, from 300 RPM to 30,000 RPM. As with any type of fan, the speed is usually based on how much power the blower will consume at maximum capacity. Low-speed models tend to require less power, which is one of the reasons they are so heavily used in air conditioning and refrigeration systems. A high-speed blower will move more air, but it may not be able to handle all of the excessive power that could come from a large compressor or other system component. [The way this article explains impeller blade speed and its relation to electrical consumption seems backwards when you consider it in terms of ceiling fans. Shouldn't high speeds translate to more powerful motors, not less? I don't think that should be the case.]

Blower Technologies ---------------

The blades on most blowers are made of aluminum or copper, though some are made of other materials such as rubber. Since these materials are relatively inexpensive, this makes them very popular. Airfoil blades are also quite common, and they do a great job of matching the shape of their respective impellers to ensure that air flows smoothly. [The author says that airfoils create an aerodynamic effect in fans by directing air flow at all angles without necessarily having to spin impeller blades. I'm guessing this is true with centrifugal fans, but it's not true in ceiling fans, since the blades on those fans rotate.]

Lightweight metal blades are the most common choice for centrifugal blowers. These blades are much more effective at creating a constant stream of air flow and are also much easier to manufacture. Another advantage of metal blades is that they can be made with swept tips, which keep air from sticking to the sides of moving blades and causing vibrations that are noisier than necessary.

Additionally, steel impellers tend to have a high strength-to-weight ratio, which combines well with their low cost and ability to cut through air efficiently. Alternatively, rubber impellers are less effective at creating a constant stream of air flow, but their resistance to heat makes them ideal for high-speed applications where durability is a key concern. [The author states that because rubber impellers don't cut through air as well and don't resist heat as well as steel ones do, they are better qualities for low-speed applications. This seems like an odd application for fans on computers. In my opinion, the best advice for computer fans is to match their speed to the power requirements of each individual fan.

Conclusion ---------------

The author of this article says that the most important thing to look for in a fan is quality. If you're just looking to keep your computers or office equipment cool, a cheap model may be suitable. For larger systems, however, spending a little more may give you better results in the long run. The author also states that air movement from blowers is nearly impossible to measure, and varies considerably from one fan to another. However, what is important is the speed and power consumption of each model.

This article seems like basic information for people who are considering buying fans for home computers or offices; however, I think it has some useful information about ceiling fans as well.