73. Why can’t the main fan regulate its flow rate by throttling at the outlet, like a pump?
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73. Why can’t the main fan regulate its flow rate by throttling at the outlet, like a pump?
This post was last edited by Zhongyuanren on 2021-11-18 at 11:24. Since the water pump controls the inlet flow rate, it creates a vacuum, resulting in cavitation that causes severe damage to the pump’s casing and impeller. To ensure that the pump chamber remains filled with water, it is necessary to control the outlet flow rate as well. If a fan is used to control or regulate flow by closing its outlet, the pressure at the fan’s outlet will inevitably increase significantly, resulting in a large pressure ratio between the outlet and the inlet, which causes the fan to surge.
1) An increased pressure drop due to outlet throttling will result in higher power consumption; the motor will take too long to start, which can lead to its damage； 2) Throttling at the outlet can easily cause the fan to spin out of control, which is very unsafe.