Compressors, Fans and Blowers are widely used in various industries. These devices are quite suitable for complex processes and have become indispensable for some specific applications. They have been defined in simple terms as below:
The basic difference between the above three devices is the way they move or transmit air/gas and induce system pressure. Compressors, Fans & Blowers are defined by ASME (American Society of Mechanical Engineers) as the ratio of the discharge pressure over the suction pressure. Fans have the specific ratio up to 1.11, blowers from 1.11 to 1.20 and compressors have more than 1.20.
Compressor types can be mainly grouped into two: Positive Displacement & Dynamic
Positive displacement compressors are again of two types: Rotary and Reciprocating
Dynamic Compressors can be categorized into Centrifugal and Axial.
Let us understand these in detail.
Positive displacement compressors use a system which induces in a volume of air in a chamber, and then reduce the volume of the chamber to compress the air. As the name suggests, there is a displacement of the component that reduces the volume of the chamber thereby compressing air/gas. On the other hand, in a dynamic compressor, there is a change in velocity of the fluid resulting in kinetic energy which creates pressure.
Reciprocating compressors use pistons where discharge pressure of air is high, the quantity of air handled is low and which has a low speed of the compressor. They are suitable for medium and high-pressure ratio and gas volumes. On the other hand, rotary compressors are suitable for low and medium pressures and for large volumes. These compressors do not have any pistons and crankshaft. Instead, these compressors have screws, vanes, scrolls etc. So they can be further categorized on the basis of the component they are equipped with.
The main difference between displacement and dynamic compressors is that a displacement compressor works at a constant flow, whereas a dynamic compressor such as Centrifugal and Axial works at a constant pressure and their performance is affected by external conditions such as changes in inlet temperatures etc. In an axial compressor, the gas or fluid flows parallel to the axis of rotations or axially. It is a rotating compressor that can continuously pressurize gases. The blades of an axial compressor are relatively closer to each other. In a centrifugal compressor, fluid enters from the center of the impeller, and moves outward through the periphery by guide blades thereby reducing the velocity and increasing pressure. It is also known as a turbo compressor. They are efficient and reliable compressors. However, its compression ratio is lesser than axial compressors. Also, centrifugal compressors are more reliable if API (American petroleum Institute) 617 standards are followed.
Depending on their designs, the following are main types of fans:
Blower is equipment or a device which increases the velocity of air or gas when it is passed through equipped impellers. They are mainly used for flow of air/gas required for exhausting, aspirating, cooling, ventilating, conveying etc. Blower is also commonly known as Centrifugal Fans in industry. In a blower, the inlet pressure is low and is higher at the outlet. The kinetic energy of the blades increases the pressure of the air at the outlet. Blowers are mainly used in industries for moderate pressure requirements where the pressure is more than the fan and less than the compressor.
Types of Blowers: Blowers can also be classified as Centrifugal and Positive displacement blowers. Like fans, blowers use blades in various designs such as backward curved, forward curved and radial. They are mostly driven by electric motor. They can be single or multistage units and use high speed impellers to create velocity to air or other gases.
Positive displacement blowers are similar to PDP pumps, which squeezes fluid that in turn increases pressure. This kind of blower is preferred over a centrifugal blower where high pressure is required in a process.
Compressors, Fans and blowers are mostly used for processes such as Gas Compression, Water Treatment Aeration, Air Ventilation, Material Handling, Air Drying etc. Compressed air applications are widely used in various fields such as Aerospace, Automotive, Chemical Manufacturing, Electronics, Food and Beverage, General Manufacturing, Glass Manufacturing, Hospitals/Medical, Mining, Pharmaceuticals, Plastics, Power Generation, Wood Products and many more.
The main benefit of an air compressor includes its usage in the water treatment industry. The waste water treatment is a complex process that requires breaking down millions of bacteria as well as the organic waste.
Industrial fans are also used in a variety of applications such as chemical, medical, automotive, agricultural, mining, food processing, and construction industries, which can each utilize industrial fans for their respective processes. They are mainly used in many cooling and drying applications.
Centrifugal blowers are routinely used for applications such as dust control, combustion air supplies, on cooling, drying systems, for fluid bed aerators with air conveyor systems etc. Positive displacement blowers are often used in pneumatic conveying, and for sewage aeration, filter flushing, and gas boosting, as well as for moving gases of all kinds in the petrochemical industries.