Impact of Design On Performance Of Industrial Centrifugal Process Fans
                     Impact of Design On Performance 
Of Industrial Centrifugal Process 
Fans
Neel Rao
Writes on Reitz India's ID Fans and FD Fans & 
Induced draft fans and forced draft fans from Reitz 
india.
Industrial process fans are used in the manufacturing industry for many applications. 
It may be truly said that no single type of fan is suitable for universal use in a 
manufacturing process plant.
Although Industrial centrifugal process fans are available in many different designs, 
all centrifugal fans have the same working principle. The volume, velocity, and 
pressure of the air delivered at the fan outlet increase with an increase in the rotor 
speed of the fan. As air is expelled from the rotor, the housing collects the air and 
directs it out in a single stream.
The industrial centrifugal fans are designed in a wide range of sizes for various 
applications. Designing a fan for a specific purpose is done by understanding the 
importance of the elements or factors that affect fan performance. A fan to suit 
specific requirements can be now be designed, due to the advances in turbine and 
jet propulsion technology. Many times ordinary tools and common materials are 
adequate to design fans capable of delivering air at moderately high pressure and 
high volume. 
Fans can be designed to meet nearly any requirement of pressure, velocity, and 
volume of air movement. Changing the speed of the wheel or adjusting the inlet or 
outlet will give the desired performance level. The need for adjustment in fans can 
differ for different fans, some need to be adjusted at their first use only, while others 
need to be adjusted at each use.
The performance and efficiency of industrial centrifugal fans are also affected by the 
number of blades used in the impeller. Generally, increasing the number of blades in 
a fan will reduce slippage and thus increasing efficiency until the point is reached 
where reduced inlet area and losses due to friction will offset gains.
The number of blades in high-pressure radial vane is less while in high volume, low-
pressure fans there are many blades. The number of blades that work well with 
different types of fans is as below:
• Commercially built radial vane fan: 5 to 12 blades
• Backward inclined impeller: 10 to 20 blades
• Curved vane squirrel cage fan: 30 to 60 or more blades
• High-pressure fan: typically, 8 blades
• High volume fan: typically, 16 blades
Many design considerations affect the performance of industrial centrifugal process 
fans, which are given below:
1. Impeller diameter and speed: With the increase in diameter of the impeller, the 
velocity of air also increases. If the impeller speed remains the same, the velocity of 
air is doubled by doubling the wheel speed.
2. Air velocity: Static pressure resists the flow of moving air and reduces its dynamic 
pressure, this dynamic pressure which is remaining is called the velocity pressure. 
The velocity pressure delivers the moving air stream.
3. Impeller width: Powerful, faster, and larger fans are needed in the pipe and 
complex duct systems where static pressure is high. The width of the impeller should 
be as high as possible when a high volume of air is the main consideration.
4. Impeller-width-to-diameter-ratio: For some high-pressure wheels, the width might 
be as little as 5% of the diameter of the wheel. The impeller width will be much 
narrower with respect to its diameter and vanes will be deeper, when high pressure 
and velocity are required.
Along with this other design consideration that affect the performance of the 
industrial centrifugal fans are the nature of air, scroll housing development, general 
proportions of fans, and power required.
About REITZINDIA
Reitz India has set a benchmark to deliver high quality fans for heavy duty industries 
which can work at precise operating conditions like high temperatures and pressures. 
Reitz offer idealistic Centrifugal Fan and Centrifugal blower design that can be used in 
all large scale process industries like cement, iron & steel, power plants, fertilizers/ 
chemicals and more.
Thank you for spending your precious time in reading this article!