What Is A Fan And A Blower?
Fan and Blowers are both mechanical devices that are meant to circulate the air. Although these two terms are often used interchangeably, fans and blowers are quite different from one another, the primary difference being their process of air circulation. Usually, these two devices are used for cooling purposes and ventilation in industries.
Let us look at some differences between a fan and a blower.
- A fan is an electrical device, while a blower is a mechanical device.
- Fans have blades that help to creates a continuous airflow and circulate the air around in every direction, whereas a blower has impellers that channel the air in a specific direction towards a particular location.
- Fans can move large amounts of air/gas at low pressure. The components of a fan are a rotor (impeller) to which the blades are attached. The impeller allows the fan to channel the airflow even at a minor change in the pressure. Fans have a specific pressure ratio of 1.1. Blowers, on the other hand, can move large volumes of air/gas at a moderate pressure setting. It comprises of a wheel attached with small blades and a casing that helps direct the airflow towards a specific location. The pressure ratio of blowers is 1.1 to 1.2.
- Fans push out the air axially, that is, the direction of airflow is along the axis of the rotor. Blowers use centrifugal force to blow out the air.
- Fans are usually smaller in size compared to blowers.
Motor Of Fan And Blower
Usually, fans and blowers have DC motors that allow you to increase or decrease the airflow very efficiently. Fan motors merely torque up the shaft of the fan which in turn causes the blades attached to it to rotate. Hence, the air circulation is confined mostly in and around the area where the fan is located. Contrary to this, blower motors use the kinetic energy created by the impellers to increase or decrease the volume of the airflow.
The efficiency of fans and blowers depend on the design of their blades and how they propel the air, that is, axially or centrifugally. In axial flow, the air that enters the fan leaves it without any change in the direction. Whereas, in centrifugal flow, the air changes direction twice, once when it enters the fan and once while leaving it.
When we talk about energy efficiency, fans consume less power than blowers and hence, are more energy efficient. But when it comes to airflow, blowers are known to produce more airflow than fans.
Apart from these factors, here are some other factors that determine the efficiency or inefficiency of fans and blowers.
- If the blower or the fan system has leaks in the ducts through which a significant amount of air can get through, the device is inefficient.
- An efficient and properly functioning blower or fan will have relatively low operating and maintenance costs.
- Silent operation is a sign of an efficient blower or fan.
- High versatility in terms of adjustment of the airflow is also a sign of efficiency.
Here is a chart that will help you better understand the efficiency of fans and blowers.
|Fan Type||Peak Efficiency Range|
|Airfoil, backward curved/inclined||79–83|
Which Is Better?
Even after considering all the above-mentioned factors, the general verdict on the Fan Vs. Blower debate is inclined in favour of the blower. One of the primary reasons behind this is that blowers are greatly energy efficient. Also, when it comes to airspeed and the rate of airflow and targeted air circulation, blowers are much better than fans. Since the cost of operating and maintaining a blower is quite less as compared to a fan, they are evidently more economical.
Types Of Fans And Blowers
Fans can be classified into two primary types:
In an axial fan, the rotating blades force the air to move in a parallel direction to the shaft about which they rotate. The air comes out of the fan in the same direction as it went it. They are a type of a compressor that creates a massive amount of airflow by increasing the pressure of the air passing through them. Usually, they require less power to operate.
Since axial fans produce a high volume of airflow at lower pressures, they are ideal for general uses. For instance, cooling cramped up rooms, offices, or confined casings as in a computer.
Centrifugal fans consist of a fan wheel and blades attached to a circular hub. As the impeller moves, it creates a kinetic energy which allows these fans to increase the volume airflow. Centrifugal fans move the air radially and change the direction of the airflow by 90 degrees. Since in these fans the air passes through an arrangement of ducts, dampers, and other components, the resultant pressure is higher than that of an axial fan.
They are best suited for high-pressure applications, for example, drying and air conditioning systems.
Like fans, blowers can also be classified into two types.
A centrifugal blower uses high-speed impellers that produce an airflow of high velocity. There are three types of blade orientation for these blowers – radial, backward curved, and forward curved. While most blowers are powered by electric motors (belt and sheave arrangement), some blowers may have with direct-coupled drive motors. Although using dampers is the most commonly used method for adjusting the speed in centrifugal blowers, it can also be altered either by resizing the sheaves or by using variable speed drives.
Positive Displacement Blowers
Positive Displacement blowers utilize mechanical force to squeeze to increase the pressure of airflow. The rotary lobe comprised of two counter-rotating lobed rotors is commonly used in these blowers. These rotating rotors move the air through the blower. Usually, positive displacement blowers are driven by direct-coupled electric motors.