what is difference between backward coved fans and centrifugal blower fans

The terms backward curved fans and centrifugal blower fans are often used to describe different types of fans, but it's important to note that backward curved fans are actually a type of centrifugal blower. So, in essence, backward curved fans are a specific subtype within the broader centrifugal fan category. Here's a breakdown of the differences:

1. Centrifugal Blower Fans (General)

• Definition: Centrifugal fans, also known as radial fans, are a type of fan that generates airflow by forcing air to move outward (radially) through the fan blades. The air is drawn into the center of the fan, then accelerated outward along the blade, and eventually expelled at a right angle to the intake.
• Structure: They typically have a circular housing that directs airflow through a spiral casing (volute). The fan's rotor has blades that push the air to the outer edges of the casing.
• Types of Blades: Centrifugal fans can have different blade designs, such as backward curved, forward curved, or radial blades. These variations in blade design affect the fan's performance characteristics, such as efficiency, noise, and pressure handling.

2. Backward Curved Fans

• Definition: Backward curved fans are a specific type of centrifugal fan, where the blades curve backward (in the opposite direction of rotation). This means the airflow is directed out of the fan in the direction opposite to the rotation of the blades.
• Design: The blades are usually curved backward at an angle, which helps minimize the amount of drag and friction that the air encounters as it moves through the fan. The backward curve design improves the fan’s efficiency and performance.
• Performance:
  • Efficiency: These fans are generally more efficient than other types (like forward curved fans) at higher airflows.
  • Pressure: They can generate higher static pressure, making them suitable for systems where resistance to airflow is a factor (e.g., air ducts).
  • Energy Consumption: They tend to consume less energy for the same airflow and pressure compared to forward curved fans.
  • Noise: They are typically quieter than forward curved fans, especially at higher speeds, because of their lower resistance and better aerodynamic performance.
• Applications: They are commonly used in applications that require high efficiency, such as in HVAC systems, industrial exhaust systems, and air handling units.

Key Differences:

1. Blade Design:
   • Backward Curved Fans: The blades curve backward, reducing drag and improving efficiency.
   • Centrifugal Blower Fans (General): Can have a variety of blade designs, such as backward curved, forward curved, and radial.
2. Efficiency:
   • Backward Curved Fans: These tend to be more efficient, especially in high-flow applications, due to the reduced drag and optimized airflow.
   • Centrifugal Blower Fans (General): The efficiency can vary depending on the type of blades used, but forward curved fans are typically less efficient at higher airflows than backward curved fans.
3. Airflow and Pressure:
   • Backward Curved Fans: Typically better at producing higher static pressure at lower to medium flow rates. They are ideal for systems that require high pressure, like air handling units with ductwork.
   • Centrifugal Blower Fans (General): Can handle a wide range of airflow and pressure, but the exact performance depends on the blade design. For example, forward curved fans typically produce lower pressure but higher flow rates.
4. Applications:
   • Backward Curved Fans: Most commonly found in industrial HVAC systems, air conditioning units, dust collection systems, and other high-efficiency, high-pressure applications.
   • Centrifugal Blower Fans: Found in a wide range of applications, including ventilation, cooling systems, and exhaust systems, with different blade types selected based on specific performance needs.

Summary:

• Backward curved fans are a specific type of centrifugal blower fan, known for their high efficiency, lower noise, and ability to generate higher static pressure at lower to medium airflows.
• Centrifugal blower fans include a broader category of fans with different blade types (backward, forward, and radial), each suited for specific performance needs.

So, backward curved fans are a more specialized, high-performance version of centrifugal fans that excel in efficiency and pressure applications.