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ASFN34771 Datasheet(PDF) 16 Page - Panasonic Semiconductor |
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ASFN34771 Datasheet(HTML) 16 Page - Panasonic Semiconductor |
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16 / 17 page  MEASUREMENT of AIRFLOW and STATIC PRESSURE Technical Information It is very difficult to measure airflow and static pressure, and there are cases where measured values vary depending on measuring devices. There are two kinds of measuring methods; double chamber method provided by JIS and AMCA (Air Moving and Conditioning Association) and wind tunnel method. Our company adopted the double chamber method, and therefore we will explain it hereinafter. The auxiliary blower (fan) adjusts an inner pressure by sucking out air. At this moment, as airflow and static pressure are varied by opening or closing the damper, each value is read on the manometer. Maximum airflow: The damper opens, and the auxiliary blower sucks out air so that static pressure becomes zero. At this moment, the pressure differential (airflow differential pressure: Pn) in chambers A and B becomes maximum. The airflow whose Pn is measured and which is determined by using the equation shown at right is called the maximum airflow. Maximum static pressure: When the damper is completely closed, the pressure in chamber A becomes maximum. At this moment, the pressure differential (static pressure: Ps) in chambers A against atmospheric pressure is called the maximum static pressure. Double chamber measuring device Ps Pn Measured fan Static pressure manometer Airflow manometer Airflow adjusting damper Auxiliary blower Nozzle Chamber B Chamber A 1. Equation Airflow Q = In the above equation, C: Flow coefficient of nozzle D: Nozzle diameter (m) γ: Air density = t: Temperature( °C) P: Atmospheric pressure(Pa) g: 9.8(m/s2) Pn: Airflow differential pressure (Pa) Ps: Static pressure (Pa) 2. Unit conversion table 1) Airflow 2) Static pressure m3/min. l/s CFM (ft3/min.) 1 16.678 35.334 0.06 1 2.1186 0.0283 0.472 1 Pa mmH2O (mmAq) 1 0.10197 9.80665 1 NOISE MEASUREMENT Operation noise is measured by hanging the fan in midair. For the DC fan, noise is measured in dB(A) 1 m from the front of the air-intake side. For the AC fan, noise is measured in dB(A) 1 m from the front of the air-intake side and the side of the fan. The background noise complies with the section in JIS B8346 that states that it should be at least 10 dB lower than the target noise reading. Our measurements were made in an anechoic chamber with a background noise of approximately 15 dB. Fan motor Microphone DC FAN MOTOR 1 m 3.281 ft (AC FAN MOTOR 1 m 3.281 ft) Fan motor Microphone AC FAN MOTOR 1 m 3.281 ft COUNTERMEASURES AGAINST MOISE Our fan motors are designed placing great importance on low noise. However, take into consideration the following points because noise is influenced depending on the mechanism design used. 1) Leave a space between the rear side of the fan suction opening and the cooled object. 2) When using two or more fan motors, leave a space between the fans. 3) According to the mounting hole dimensions (page 22), design so that the mounting face and blades are not crossed. 4) Grease in the bearings will deteriorate and noise will gradually increase as the fan is used. The replacement period will differ depending on the conditions of use and allowable sound level. We recommend periodic replacement. 02/2006 16 |
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