DC FAN

   Determination of the air performance curves is obtained by using the double chamber method based on  AMCA

 standard. The difference between the pressures before and after the nozzle (differential pressure Pn )is measured

 to obtain the air flow at the nozzle and the different pressure between thoser in the two chambers (static pressure

 Ps ).The air flow is calculated from the differential pressure by using equation (A). The auxiliary blower cancels

 out the aerodynamic resistance.

    Q = 60 AV .... (A)

     Were

           Q : Air flow rate (m³/min) 

           A : Nozzle sectional area = F/4 D² (m²)

           V : Average flow velocity from nozzle =

                                                               r : Specific fravity ( kg/m³) of air ( r=1.2kg/m³ at 20C, 1 atm)

                                                               g : Gravitational acceleration = 9.8 m/S²

                                                               Pn : Differential Pressure (mm H²O )

                                                               Ps : Static pressure (mm H²O )

    Maximum air flow : When opening the nozzle and absorbing the air using the auxiliary blower to make the static

 pressure zero (Ps=0), the differential pressure (Pn )between chamber A and chamber B will be the    maximum. The

 air flow obtained by applying the differential pressure (Pn) to the above equation can be called the maximum air

 flow.

    Maximum static pressure : A shown in the above figure, when closing the nozzle, the pressure in the chamber A

  will be the maximum. This differential pressure (Ps) between the pressure and the pressure in the chamber A

  can be called the maximum static pressure.