How to Calculate the Specific Speed and ψ and φ Values of a Cabinet-Type Centrifugal Exhaust Fan

How to Calculate the Specific Speed and ψ and φ Values of a Cabinet-Type Centrifugal Exhaust Fan

Specific speed is a term commonly used when discussing the performance of cabinet-type centrifugal exhaust fans. Generally speaking, it refers to the speed at which a series of cabinet-type centrifugal exhaust fans operate most efficiently. Specific speed is related to the specific speed ratio. It can be used as a benchmark for measuring the relationship between fan performance and airflow. Additionally, it can be used to determine the shape of the impeller and the type of cabinet-type centrifugal exhaust fan. Next, the displacement method is used to determine the values of specific speed ψ and φ, and two cabinet-type centrifugal exhaust fans are prepared for this test. First, parameters such as ambient temperature, atmospheric pressure, and the diameter of the first impeller must be obtained, along with the fan speed, total pressure efficiency, airflow, and static pressure of the first fan, as well as the diameter of the second impeller, the speed of the second fan, and its total pressure efficiency. Then, based on the above known parameters, substitute the square of the cabinet-type centrifugal exhaust fan’s diameter into the formula π/4. The outlet area of the first fan is 0.1544 m²; the average outlet velocity of the first fan is 5.374 m/s, relative to the outlet area of the cabinet-type centrifugal exhaust fan; the effective dynamic pressure of the first fan is 1/2 times atmospheric pressure multiplied by the square of the average outlet velocity, resulting in 16.27 Pa. The total pressure of the first fan is the sum of the fan’s static pressure and the effective dynamic pressure of the cabinet-type centrifugal exhaust fan, which is likely 191.4 Pa. The fan’s static pressure at standard temperature and pressure is 176.4 Pa, and its specific speed is 141.4 rpm. Based on the above formula, calculate the total pressure coefficient and flow coefficient for the cabinet-type centrifugal exhaust fan. When entering values, be sure to replace the existing values with the new ones.