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Axial fan – Centrifugal fan – Flow rate calculation
Whether we are in production plants, assembly lines, spray booths or engine test booths, air quality inside these environments must be checked and cleaned to ensure the wellness of the workers; nowadays, modern plants which want to obtaining fresh air in industrial environments use the industrial fan.
Industrial fans help air recirculation in environments where there’s a need for clean air. They often work as vacuums for harmful or flammable substances, as in spray booths.
Fans have a very long history, dating as far back as 500 b.C. in India where they were called Punkah. It was a fully manual system, and servants had to activate the big fan, by pulling some ropes connected to very big leaves of a plant named Palmyra. Omar-Rajeen Jumala in 1832 built the first real mechanical fan; it was used and tested in coal mines.
In this video we’ll show you the different types of industrial fans, their features and how they work.
Industrial fans are divided into 4 categories:
- Axial fans
- Centrifugal fans
- Tangential and helicocentrifugal fans
We’ll focus on the axial and centrifugal ones, the most frequently used in industrial plants.
In axial fans, gas is aspirated and sent towards the same direction, parallel to the axis of the impeller. The impeller, the rotating organ of all fans, is made of inclined blades attached to a central hub; when the whole group starts spinning, the blades push the air thus creating a difference in pressure. In an axial impeller, if blades spin clockwise the direction of the flow will be forward, whereas if they spin counterclockwise the flow will reverse its direction.
The advantages of this type are: speed (higher than the other types), higher dynamic pressure, and the fact that it’s smaller, lighter and cheaper.
Let’s now focus on centrifugal fans ; the flow gets aspirated in parallel to the impeller, but gets pushed perpendicularly thus creating a 90° angle. If we observe its components we’ll find: the inlet flange, which always integrates a protective grate; the inlet cone, designed as a Venturi tube, to increase the speed of entry flow. Then we find the impeller, located inside of a snail-shaped structure in sheet metal; this design makes the centrifugal factor to increase. The transmission shaft with its relative bearings, moved by a system of pulleys connected to a belt, activated by a three-phase electric engine.
As we can see in the animation, the engine activates pulleys, which make the transmission shaft spin; pulleys have a different diameter, and they have the task to transmit energy and decrease engine revolutions, a minor speed translates in bigger strength, so an increase of the couple. The shaft makes the impeller spin, creating a centrifugal effect in its core, the flow arrives perpendicularly to the axis of the impeller, which distributes the flow radially, creating some kind of vortex; the flow, helped by the spiral geometry of the structure, is directed towards the exit hole at a higher pressure which allows it to travel greater distance through a piping system.
Whether we are in production plants, assembly lines, spray booths or engine test booths, air quality inside these environments must be checked and cleaned to ensure the wellness of the workers; nowadays, modern plants which want to obtaining fresh air in industrial environments use the industrial fan.
Industrial fans help air recirculation in environments where there’s a need for clean air. They often work as vacuums for harmful or flammable substances, as in spray booths.
Fans have a very long history, dating as far back as 500 b.C. in India where they were called Punkah. It was a fully manual system, and servants had to activate the big fan, by pulling some ropes connected to very big leaves of a plant named Palmyra. Omar-Rajeen Jumala in 1832 built the first real mechanical fan; it was used and tested in coal mines.
In this video we’ll show you the different types of industrial fans, their features and how they work.
Industrial fans are divided into 4 categories:
- Axial fans
- Centrifugal fans
- Tangential and helicocentrifugal fans
We’ll focus on the axial and centrifugal ones, the most frequently used in industrial plants.
In axial fans, gas is aspirated and sent towards the same direction, parallel to the axis of the impeller. The impeller, the rotating organ of all fans, is made of inclined blades attached to a central hub; when the whole group starts spinning, the blades push the air thus creating a difference in pressure. In an axial impeller, if blades spin clockwise the direction of the flow will be forward, whereas if they spin counterclockwise the flow will reverse its direction.
The advantages of this type are: speed (higher than the other types), higher dynamic pressure, and the fact that it’s smaller, lighter and cheaper.
Let’s now focus on centrifugal fans ; the flow gets aspirated in parallel to the impeller, but gets pushed perpendicularly thus creating a 90° angle. If we observe its components we’ll find: the inlet flange, which always integrates a protective grate; the inlet cone, designed as a Venturi tube, to increase the speed of entry flow. Then we find the impeller, located inside of a snail-shaped structure in sheet metal; this design makes the centrifugal factor to increase. The transmission shaft with its relative bearings, moved by a system of pulleys connected to a belt, activated by a three-phase electric engine.
As we can see in the animation, the engine activates pulleys, which make the transmission shaft spin; pulleys have a different diameter, and they have the task to transmit energy and decrease engine revolutions, a minor speed translates in bigger strength, so an increase of the couple. The shaft makes the impeller spin, creating a centrifugal effect in its core, the flow arrives perpendicularly to the axis of the impeller, which distributes the flow radially, creating some kind of vortex; the flow, helped by the spiral geometry of the structure, is directed towards the exit hole at a higher pressure which allows it to travel greater distance through a piping system.
The impeller is the main components of fans, its shape ensures different performances and uses.
The radial blades fan is the most resistant structure for this field. They are made to be durable, resistant and powerful, useful to move big quantities of air, for they reach very high pressures; these fans have a very low maintenance cost and they are perfect for an initial cheap solution.
The airfoil fan, similar to the ones we find in airplanes, has the best performances with the lowest consumption; it can be used in environments where there are hard, abrasive or harmful dusts but the fan must be made of special materials.
The industrial fan with reversed blades shows up with a minor number of longer blades made of sheet metal with constant thickness; it’s a cheap solution with a lower performance, they are used for air renewals and small quantities of dust.
Industrial fans with forward blades are characterized by a higher number of small blades close together, facing the direction of the rotation; they can move large volumes of air at low speed and they are recommended for applications where a constant air flow rate or an air delivery with constant pressure is necessary.
“industrial ventilation systems” are a combination of different products: mainly a fan, which can be axial or centrifugal, and a piping network for gas passage, from the outside to the inside or vice versa. When an industrial ventilation system is installed, there is an important feature to take into account, that is, how much gas do we want our plant to carry? To know this value we have to calculate the flow rate of our plant, namely “the volume of gas that the fan moves in a certain period of time”. In the international system, flow rate is measured in m3/s, the formula to know the flow rate of an implant is very simple: by knowing the speed of the carried gas, namely V, and multiplying it for the width of our piping, namely A, we obtain the flow capacity expressed in m3/s. Knowing this value for ventilation implants is essential, it helps us understand whether we are installing the correct product for that determined process.
Let’s assume that we have to run a spray booth which uses burners to generate hot air; burners need a right amount of air to work optimally. Let’s suppose we install an industrial fan with a flow rate of 400 m3/s, and we realize that the maximum temperature level in the booth isn’t reached, causing disruptions in productions; this means burners don’t get the right amount of air they need, a problem that can be solved with an appropriate adjustment to the ventilation system. In order to obtain a higher air flow rate, two factors require an adjustment: to install a bigger and more powerful fan, and to replace the pipes with others of bigger width; flow rate will be greater by running the burners at maximum power.
In this video we saw how the various types of industrial fans work, where they are installed and how to choose the right one for the type of process.
The radial blades fan is the most resistant structure for this field. They are made to be durable, resistant and powerful, useful to move big quantities of air, for they reach very high pressures; these fans have a very low maintenance cost and they are perfect for an initial cheap solution.
The airfoil fan, similar to the ones we find in airplanes, has the best performances with the lowest consumption; it can be used in environments where there are hard, abrasive or harmful dusts but the fan must be made of special materials.
The industrial fan with reversed blades shows up with a minor number of longer blades made of sheet metal with constant thickness; it’s a cheap solution with a lower performance, they are used for air renewals and small quantities of dust.
Industrial fans with forward blades are characterized by a higher number of small blades close together, facing the direction of the rotation; they can move large volumes of air at low speed and they are recommended for applications where a constant air flow rate or an air delivery with constant pressure is necessary.
“industrial ventilation systems” are a combination of different products: mainly a fan, which can be axial or centrifugal, and a piping network for gas passage, from the outside to the inside or vice versa. When an industrial ventilation system is installed, there is an important feature to take into account, that is, how much gas do we want our plant to carry? To know this value we have to calculate the flow rate of our plant, namely “the volume of gas that the fan moves in a certain period of time”. In the international system, flow rate is measured in m3/s, the formula to know the flow rate of an implant is very simple: by knowing the speed of the carried gas, namely V, and multiplying it for the width of our piping, namely A, we obtain the flow capacity expressed in m3/s. Knowing this value for ventilation implants is essential, it helps us understand whether we are installing the correct product for that determined process.
Let’s assume that we have to run a spray booth which uses burners to generate hot air; burners need a right amount of air to work optimally. Let’s suppose we install an industrial fan with a flow rate of 400 m3/s, and we realize that the maximum temperature level in the booth isn’t reached, causing disruptions in productions; this means burners don’t get the right amount of air they need, a problem that can be solved with an appropriate adjustment to the ventilation system. In order to obtain a higher air flow rate, two factors require an adjustment: to install a bigger and more powerful fan, and to replace the pipes with others of bigger width; flow rate will be greater by running the burners at maximum power.
In this video we saw how the various types of industrial fans work, where they are installed and how to choose the right one for the type of process.