​Series Operation of High-Pressure Centrifugal Exhaust Fans

Series Operation of High-Pressure Centrifugal Exhaust FansCertain engineering applications require connecting two or more high-pressure centrifugal exhaust fans in series, as a single unit may not meet production demands. Similar to centrifugal pumps, connecting high-pressure centrifugal exhaust fans in series increases air pressure, while parallel connection boosts airflow. So, what exactly is this connection? In practice, two or more high-pressure centrifugal exhaust fans are connected end-to-end, then transport gas into the ductwork. This is called series operation. Typically, one fan is positioned before the equipment, while the other is placed after the equipment in a series configuration. In air conditioning systems, installing fans in both the supply and return ducts creates such a high-pressure centrifugal exhaust fan series system. If two identical high-pressure centrifugal exhaust fans are used, the system's total air volume equals the individual air volume of each fan, and the air pressure is the combined total of both fans. Under these operating conditions, the performance curve for series-connected high-pressure centrifugal exhaust fans is obtained by vertically superimposing the air pressure at identical flow rates. Consequently, when two fans operate in series, the system's air pressure increases. Each fan possesses sufficient capacity to convey greater gas volumes through the ductwork, resulting in a combined airflow rate Qc that exceeds that of a single fan (L). When fans operate separately, airflow QB and pressure are inversely proportional. To effectively increase pressure, higher duct resistance steepens the duct system's characteristic curve, enhancing the boost effect. Thus, high-resistance ducts must employ a series configuration of high-pressure centrifugal exhaust fan units. Failure to do so will not achieve satisfactory pressure enhancement. Particular caution is required when connecting two high-pressure centrifugal exhaust fans with differing efficiencies in series. If installed incorrectly, the suction inlet of the larger fan will have insufficient airflow, causing reduced air pressure and preventing the series-connected fans from operating normally.