There are two test methods "24V DC Cooling Fan" air volume and pressure, one instrument with wind tunnel testing, the other is measured by double box. But for the average user, there is no such device, according to data provided by the manufacturer only as a reference, the ventilation area is subtracted from the outlet area of the tongue at the projected area of the vortex, the plane speed velocity gas flow through the entire plane, the unit is m3 / s, flat-rate constant, "24V DC Cooling Fan" blade impeller diameter, the greater the area through the purchase, the greater the amount of wind, the plane's speed and the speed of the child decide just pressure. When the ventilation area must, flat rate, the greater the amount of wind. The larger the amount of wind, the greater the heat absorption of air, the air flow can take more heat transfer, "24V DC Cooling Fan" fan thermal effect is more obvious.