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What Is A Centrifugal Fan? – Complete Guide
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A centrifugal fan is one of the most efficient fans on the market today. Most people think of a centrifugal fan as just a fan; its intricacies are not exactly common knowledge.


    This complete guide will tell you everything you need to know about centrifugal fans. You might be wondering ‘What is a centrifugal fan? What are centrifugal fans used for? What are the different types of fans?


    We will answer these questions and more. We’ll also highlight several useful videos from HVAC experts who break down these concepts in great detail.


    A centrifugal fan or centrifugal blower is a pump or motor that moves air. It pulls the air inside the blower and then pushes it out at a 90o angle. The two main components of a centrifugal fan are the motor and the impeller. An impeller sucks or pulls air, in contrast to a propeller which pushes air.


    Some fans can pull and push air at lower than a 90o angle; these fans are called mixed flow fans.


    Centrifugal fans can either have no exterior housing or structure to offer protection or they can be built with some protective housing.


    As shown in the video below, there are five different types of centrifugal fans, which differ based on the type and shape of the fan blades.


    Backward curved blades


    Backward inclined blades


    Backward inclined aerofoil blades


    Radial blades


    Forward curved blades


    Know the Working of an Axial Fan


    Across industries, there are various machines and devices both electrical and electronic, which are designed for 24/7 working. As a result, they heat up, and if this exceeds the limits set, the device may be damaged which will result in halted production. To avoid machine failure due to excess heat, AC or DC industrial fans are used. There are various types of fans such as centrifugal, axial, and so on. An axial fan is a type of industrial fan which helps cooling of machines and devices. They facilitate parallel air flow to the rotor shaft, which offers ventilation to the device and prevents overheating. This post discusses the working and uses of AC and DC axial fans.


    How Does an Axial Fan Work?


    The industrial fan is chosen based on the direction of the air flow. an axial fan comprises a rotator shaft, blades, impeller, and a housing mostly made of steel. There is an air inlet through which the air enters inside once the rotator shaft rotates. The air flows parallel to the rotor shaft in a linear manner. This increases the flow rate and can gush in and out huge volumes of air. This can be achieved keeping both the pressure and power consumption low. The air enters the impeller in an axial direction. To raise the flow rate, the blades push the impeller and further deflect the flow of air into the guide vane. The air flow from the guide vane again becomes axial and enters the diffuser tube. The kinetic energy of the moving blades is converted into pressure which facilitates the required amount of ventilation. The blades of the axial fan are fixed but can be adjusted in terms of spacing and angle which helps achieve the required flow rate.


    The shape of the blades to some extent also affects the speed of air flow. In axial fans, these blades may be tilted forward, backward, or could be curved. The number of blades may vary from 2 to 20, and the power or motor capacity required to drive operate these fans depends on the number of blades, speed and volume of air flow, and other application requirements. These fans produce pressure difference and force to facilitate the flow of air through them. Depending on the power supply and the application size, you could choose either a DC axial fan or AC axial fan.


    Why high pressure fans are often used in pig barns


    Various ventilation techniques are used  to raise the air quality in pig barns to a desired level. Many of these techniques use a specific type of fan to facilitate the required air movement. A frequently used fan in pig barns is the High Pressure Fan. In this article, we will tell you more about High Pressure Fans and why these fans are often used in pig barns.


    Fundamentally, High Pressure Fans are used in:


    High resistance systems


    Systems in which the fans must have sufficient negative pressure or positive pressure build-up at lower power and speed


    1. Overcoming high resistance


    In most pig barns, each section has its own ventilation system, which provides minimum and maximum ventilation. With a standard ventilation system, the resistance ? P Stat to be overcome in the barn can be around 40 Pa and rise to at least 80 Pa (depending on the system). For such systems, we use a standard range of Axial Fans. Examples of this type of fan are Panel Fans and Tube Mounting Fans. There are, however, systems where, among others, air washers, heat exchangers and air filters cause the negative pressure or positive pressure (? P Stat) to be overcome to rise well above 80 Pa. For these applications, we use High Pressure Fans.


    2. Stable negative pressure when regulating fan speed


    As the conditions inside and outside a barn change daily, a ventilation system must be flexible. In addition, growing pigs are also a changing factor. This means that the amount of air must be variable. It is important to dissipate heat, moisture and ammonia, but primarily to supply oxygen. One of the characteristics of High Pressure Fans is that even when the fan speed is adjusted, they still provide an acceptable pressure build-up. As previously explained in our blog, The fan laws, we see that when regulating the fan speed, the flow (M3/h) is linear and the pressure ? P Stat (Pa) decreases quadratically while the power consumption (Watt) even decreases to the 3rd power.


    



    Industrial centrifugal fan plays an important part in cement production line, especially with the development of preheater pre decomposition kiln, even more important. At the same time the fan is also more power consumption of cement equipment, according to statistics, the total power of about 15% of the total installed capacity of cement plant.


    What is the role of fan in the cement production line? 


    High temperature fan: the equipment through the raw material and clinker, Inlet temperature can reach 320℃, is to pre-heater vacuum pumping, the raw material in the preheater down the process of full preheating (material to go down, hot air to go up), while the tower pull over the wind to the raw material mill for Heat, so its shutdown will directly lead to raw material grinding system and firing system shutdown.


    Cement plant kiln exhaust fan: to make high-temperature fan and vertical mill system exhaust out of the dust after the row to the atmosphere.


    Kiln centrifugal blower: it is similar to cement plant kiln exhaust fan, high energy saving,less power.


    Dust collector fan: fan is the main equipment in dust removal systems, offer the power source of the whole systems, and overcome the resistance loss caused by the air flow in the system.


    



    A suction axial flow fan is a type of industrial fan used to cool machines and equipment which heat up after use. Axial flow fans are the type of compressor, which produces airflow parallel to the axis, thus the name. These fans are equipped with impellers, which suck the air in and discharge in the same direction of the axis.


    There are AC as well as DC axial flow fans. It may be designed in different ways such as with a duct or a mounting ring, and so on, depending upon the requirement. So, there are different standard designs which can be customized based on your device and installation type. The materials and accessories used for the fan are decided on these and other physical factors such as the environment it would be exposed to, temperature, moisture, pressure, and so on. This post discusses various designs of axial flow fans, and general features.


    Components of Axial Flow Fan


    The most basic part of an axial flow fan is the motor. Other than that it has ball bearings, blades, and impellers. The fan has a housing or an enclosure which protects it from external damage, spillage, shock, vibration, and so on. The enclosure is metallic and made of steel, aluminum, or alloys. The impellers are usually made of cast aluminum with black paint, thermoplastic, or steel, and designed to be corrosion resistant. The thermoplastic impellers are generally not considered ideal for commercial applications, so they are usually reserved for residential applications. The propellers feature blades. There can be 2 to 20 blades on the propellers.  The fan is connected to a motor drive, which is usually placed in a housing parallel to the direction of airflow. The blades are usually made of aluminum. These fans are designed to be resistant to extreme temperatures, flames, shock, corrosive materials, and so on. A few common accessories of this fan include suitable connecting points, silencer, protection grill, counter flange, vibration controller, feet for the required positioning, and a variable inlet vane.


    Design of Axial Flow Fans


    As mentioned, the fan has various standard designs. Here are a few pointers:


    The fans may be duct mountable or wall mountable.


    Ducted fans have a duct through for a seamless airflow.


    The ring mountable fans allow the airflow from one big enough area to another; so, it is suitable for large spaces.


    The circulator fan has rotating impellers, which are typically used in ceiling fans.


    Axial flow fans offer large airflow rates at low pressures because of their working principle. The blades of these fans draw air parallel to its axis and move it in the forward in the same direction within the axis of the fan.


    How Does an Axial Flow Fan Works?


    Axial fans work similar to an aircraft wing, which possesses an airfoil shape and produce lift. Due to the airfoil shape of the wing, the air above and below it are divided and have different air velocities. This is because the air in above section travels farther than air in the bottom section. The air above has a high air velocity, which produces a high dynamic force and low static pressure. Against this, the air in the below section has low air velocity and produces a high static pressure. These pressure differences create the lift. Now coming to the axial fan, the blades of the propellers act like wings and they push air forward, thereby causing a lift. As a result of this lift, the air is propelled, as well as pushed back. The speed of air continues to increase up to a point even after the air leaves the fan. The airflow is great at the exit than at the entry point.
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