Airflow Vs Pressure
How to Measure the Airflow vs. Pressure
It is very difficult to measure the air performance. The measurement varies by method. There are two methods to measure the static pressure and the airflow. One is wind tunnel and the other is the double chamber method.
The performance specification of airflow and static pressure shown in this data book is measured using the double chamber method. Here, we would like to explain the double chamber method. (See Figure #1) The variable exhaust system adjusts the air density by drawing out the air. Sudden opening of the nozzle induces the instantaneous change of the static pressure and the air flow. The pressure of each manometer is then read.
Figure1. The measuring method - double chamber
Maximum Air Flow is measured under the condition of zero static pressure created in chamber B by the variable exhaust system At this point, the difference in air pressure between chamber A & B is measured with the fan running and the nozzle open.
Maximum Static Pressure is measured with the fan running in chamber A with the nozzle shut. This creates a sealed box in which static pressure reaches its maximum value. The static pressure value is the difference between the maximum pressure and atmospheric pressure in chamber A.
Actual measurement is recorded when the fan speed is stabilized at rated voltage.
The Air-flow Conversion Table
The Static Pressure Conversion Table
The static efficiency of a fan is the volumetric flow rate multiplied by the static pressure and divided by the input electrical power. The fan is defined to include the motor, impeller, and frame ; therefore, this efficiency includes both the electromechanical efficiency of the motor and the aerodynamic efficiency of the impeller and frame