Centrifugal fans are essential components of ventilation and air conditioning systems, pushing air through ducts and managing interior air quality. Forward curved and backward curved fans are two prominent types of centrifugal fans that are often utilised in HVAC applications. Understanding the distinction between these two types of fans is critical for picking the best fan for a given application. We will analyze the difference between forward curved and backward curved fans in this guide.
What Is Forward Curved Fan And How It Works?
A centrifugal fan with forward curved blades is a type of fan that circulates air or gases in a circular motion using a series of curved blades. The blades are linked to a central hub driven by an electric motor. These fans are widely used in a variety of industrial operations, ventilation systems, and air conditioning systems.
A forward curved centrifugal fan’s major characteristics include its small size, high efficiency, and low noise levels. The curved blades can circulate a large volume of air at low velocities, which minimises noise levels. These fans are also relatively small in size, allowing them to be used in small spaces.
Flow from the impeller is created in a tangential direction for this type of impeller. The forward curve of the blade gives kinetic energy to the air, necessitating the use of a scroll housing to convert the kinetic energy to static pressure. For any given steady speed, the input power characteristic rises as flow increases from zero to maximum. At greater flow rates, care must be taken to ensure that the load presented by the impeller does not exceed the rating of the driving motor.
Applications Of Forward Curved Fan
Forward curved impellers are commonly employed in tiny installations to offer substantial air volumes at low operating speeds. They are also appropriate for applications requiring continuous airflow or constant pressure supply. Domestic boilers, warm air heaters, radiant heat tube heaters, refrigeration, heating fan coil assemblies, and many other applications employ forward curved fans.
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What Is Backward Curved Fan And How It Works?
Backward curved impellers often have fewer longer blades that face away from the direction of rotation. The blades bend rearward from the inner to the outer edge, relative to the rotational direction, and can be plate or aerofoil in shape.
Because the impeller creates static pressure throughout the greater length of the blade, flow is created in a radial direction. A positive pressure is created on the front side of the blade, forcing the air outwards, while a negative pressure is generated on the reverse side of the blade. This negative pressure drags air into the gap, which the front side of the next blade takes up and pushes outwards. As a result, it may be utilised with or without a scroll expansion housing, combining a reasonably steep pressure profile across the regular operating range with a power profile that does not overwhelm the drive motor at higher flow rates.
Applications Of Backward Curved Fan
Backward curved impellers are often used in high-efficiency, high-pressure applications when overall system efficiency is important or a scroll housing is not required.
Backward curved fans are used in a variety of applications such as high pressure condensing (premix) boilers, extract ventilation systems, fume extraction systems, gas burner systems, heat recovery systems and many more.
Final Opinions
Based on their design features, both forward curved and backward centrifugal fan have distinct benefits and drawbacks and are appropriate for a variety of applications. When selecting the proper fan for a certain application, several elements must be considered, including air volume, pressure, energy efficiency, noise level, and maintenance needs.
