Relationship between flow rate and head of variable frequency pumps
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This post was last edited by scord on 2016-6-2 at 11:33. The flow rate range of a certain pump is 2000~6000 kg/hr, with a head of 50 m. Originally, a power-frequency motor was chosen; now, a variable-frequency motor is planned to be selected. According to the pump head theory, the head is proportional to the square of the rotational speed, while the flow rate is proportional to the rotational speed; in other words, the head is proportional to the square of the flow rate. If I want to ensure that the pump has a head of 50 m at a flow rate of 2000 kg/hr, then what will be the head at a flow rate of 6000 kg/hr? (Assuming the frequency range of the variable-frequency motor meets the requirements)
Head is only used to determine the pump; once the piping and the pump have been chosen, head becomes irrelevant – the head value is determined by the level of resistance present. Our goal is to ensure traffic
The pipeline resistance caused by changes in flow rate actually does not change much; the head is primarily used to overcome the pressure drop in the intermediate equipment and to achieve the operating pressure required by the downstream equipment
I don’t want the pressure at the pump outlet to change too much, otherwise the pressure ratings of the downstream pipes, equipment, and instruments will all need to be increased
A variable-frequency pump regulates flow by changing frequency; head is proportional to the square of the rotation speed. If the rotation speed changes, wouldn’t that inevitably affect the pump’s head as well?
Since the work done remains constant, logically, as the flow rate increases, the corresponding head should decrease, right?