Types of Fans

There are very many types of fans available in the market. This variation is based on the following key factors: space limitations, material types, efficiency, pressure and volume flow amongst other factors. It is upon the end user to specify the exact specifications he/she requires.

All the existing fans in the market can be classified in the following two categories: the centrifugal and the axial flow fans. This difference is based on the movement of air from the time it reaches the blades and the time it leaves.

The centrifugal fans are designed such that; the flow of air is forced to change direction twice. That is, when it enters and leaves the fan. This results in radial, forward and backward curved flow. In the axial fans, air enters and leaves the fan without changing its direction. These two main aspects clearly indicate that these types of fans are different in their performance and efficiency.

Taking a look at the efficiencies of these fans, it is quite evident that centrifugal fans have the highest efficiencies of between 79% and 83% for an inclined fan.  On the other hand, the vane axial fans can only attain between 78% and 85% efficiency. On the lower end, the forward curved centrifugal fans have the lowest efficiency of between 60% and 65%. The propeller axial fans have the lowest efficiency, which range between 45% and 50%.

Types of fans and their applications

The three main types of centrifugal fans include:

1. The radial fans; they are used in industrial applications due to their high static pressure. They are suitable for medium speeds and high temperature applications. They are mainly used to handle heavily contaminated air streams.
2. The forward-curves; these fans are used in high airflow applications. They can move high volume of air in low pressure. They are suitable for low temperature and clean environment operations.
3. The backward-inclined fans; they are non-overloading and they are most efficient centrifugal.

The axial flow fans are commonly used in a number of domestic and industrial applications. The types of fans in this category include:

1. The tube axial fans are mainly used in high pressure applications. They can handle a pressure of up to 400 mm WC.
2. The vane axial fans; the only difference between these fans and the tube axial fans is the guide vanes. They improve the efficiency of the fan and handle a pressure of up to 500 mm WC.
3. The propeller fans are operated at low temperature and low speeds. They can operate at low pressure with the ability to handle large volumes of air.

These types of fans are designed for specific applications. It is upon the end user to select one that can guarantee optimal performance.