Fan air volume, wind pressure, power and speed of the relationship and related calculations, fan selection

Fan efficiency (η1)

National standards require that the efficiency of a single fan should not be less than 60%, usually 0.7 to 0.8, the higher the efficiency of the fan, the less energy waste and loss during operation.

Mechanical transmission efficiency (η2)

It is the core index of the evaluation of the transmission system, which is directly related to the transmission mode of the fan and the motor, and the direct-connected η2 is 1, the axial coupling η2 is 0.95~0.98, the triangular belt η2 is 0.9~0.95, and the flat belt η2 is 0.85.

Motor capacity factor (K)

Also known as the reserve coefficient, the greater the coefficient, the stronger the reserve capacity of the motor, the weaker the vice versa, under normal circumstances, the motor capacity coefficient is between 1.1-1.3, the small power takes the large value, the high power takes the small value.

Fan selection and application The relationship between wind pressure, air volume and power and speed

The fan and pump load is a typical variable rotation load, that is, the air volume is proportional to the speed, the rotation or wind pressure is proportional to the square of the speed, and the shaft power is proportional to the cube of the speed. Changes in these parameters, such as wind pressure (P), air volume (Q), power (N) and speed (n), will directly affect the performance and efficiency of fan operation. The following is a detailed description of the relationship between these parameters.

Fan speed refers to the number of rotations of the fan impeller Per Minute, usually expressed as rpm (Revolutions Per Minute). Under normal circumstances, the speed of small fans is higher, and the speed of Large Fans is lower.

Relation between speed (n) and air volume (Q)

An increase in speed (n) leads to an increase in air volume (Q). The faster the speed, the more air inhaled, the greater the output air volume, and the air volume is proportional to the speed.

Relation between speed (n) and wind pressure (P)

An increase in speed (n) leads to a rapid increase in wind pressure (P). When the speed increases, the wind pressure will increase in proportion to the square of the speed, and the wind pressure is proportional to the square of the speed.

The relationship between speed (n) and power (N)

An increase in speed (n) leads to a maximum increase in power (P). When the speed increases, the power will increase in proportion to the cube of the speed, and the power is proportional to the cube of the speed.

The relationship between air volume (Q) and wind pressure (P)

Air volume (Q) and air pressure (P) are two important parameters of fan performance, and there is no simple linear relationship between them. For example, when the volume of air increases, the wind pressure may decrease; When the wind pressure of the fan increases, the air volume may decrease.