Air volume & wind pressure.

Air volume: air volume is refers to the speed rate of planar of fan ventilation area. Ventilation area is the projection area of the outlet area minus vortex tongue. Plane speed is gas velocity of the airflow through the whole plane, unit is the m3 / s. Plane  speed is constant, outer diameter of fan impeller will larger, the greater the ventilated area, then the air volume is also larger. The plane speed is determined by the rotor speed and wind pressure. When a certain ventilation area, the greater the plane speed, air volume is larger. The bigger air volume and air heat absorption capacity, and the air flow transfer can take weeks & to take more heat, fan heat effect is more obvious.

Wind pressure: for normal ventilation, need to overcome the resistance inside the fan ventilation trip, fan must have overcome the pressure of the air resistance, the change of the measured pressure value, called static pressure, the maximum static pressure and atmospheric pressure differential pressure .It is the gas pressure, the role of parallel to the surface static pressure is measured through hole perpendicular to the surface. What we need in the gas flow kinetic energy change into pressure form called dynamic pressure.

To achieve the purpose of the air supply, it is necessary to have static pressure and dynamic pressure. Total pressure is the algebraic sum of static pressure and dynamic pressure, total pressure refers to the total increasing pressure given by the fan, namely the total difference pressure between exports and imports. In practical applications, the nominal maximum wind quantity is not the actual fan heat get delivery, air volume is big, does not represent the high ventilation ability. Due to air flow, air flow in the flow path will meet fan heat collection or element block, the impedance will limit the free flow of air. Increase the air volume, air pressure will decrease. So there must be a best operating point, namely intersection of the fan performance curve and wind resistance curve, In working point, the fan characteristic curve slope is least, and the system characteristic curve of the lowest rate. Note that the fan static efficiency (airflow by air pressure present electricity) is the best. Sometimes, of course, in order to reduce system impedance, even use smaller fan, can also get the same air volume.