A big horse can’t pull a small cart
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When teaching the principles of chemical engineering, the teacher mentioned such a phenomenon. As stated in the question, those who know why this happens can please explain it: why can a pump with a high flow rate fail to achieve the required flow rate? For example, a pump with a flow rate of 25 liters per minute and a head of 15 meters may not be able to deliver a flow rate of 2 liters per minute, while a pump with a flow rate of 3 liters per minute can indeed achieve a flow rate of 2 liters per minute. If anyone knows the reason, please let me know. Thank you
It is guessed that pump 1 is a reciprocating pump, pump 2 is an axial flow pump, pump 3 is a centrifugal pump, and pump 4 is a screw pump. High flow rate refers to the rated flow rate at the rated head (at the point of maximum efficiency); in practice, the flow resistance in the small pipes at the rated flow rate is certainly much higher than the rated head, resulting in a significant decrease in flow rate. The small pump has a high head, which can meet the system’s resistance requirements; thus, the flow rate is guaranteed