Regarding the head capacity of centrifugal pumps
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Suppose there is a centrifugal pump with a head of 10 m and a default friction loss of 0; then to what height can this pump lift a liquid with a density of 800 kg/m3? That is, the head converted into a liquid. Is it 12.5 or 8m? I asked a master, and he said that head is inversely proportional to density; I don’t think that’s correct, so I’m seeking advice.
Head is an inherent property of centrifugal pumps that remains constant; it represents the work done by the impeller on each unit mass of fluid, and is generally conceptualized as the height to which the fluid can be lifted. So, no matter what medium is used, the head remains unchanged. When pumping water, the density is low, so it sprays high ； When spraying liquids with high density, the spray distance is low. But the head is the same. Generally, the nameplate of a centrifugal pump indicates the height it can lift when water is used as the fluid.
Head is the work done by a pump on a unit volume of fluid from the inlet to the outlet, and it remains constant regardless of the type of fluid being pumped. But generally, we understand head as the height that can be reached; strictly speaking, what we usually refer to is not head. The height to which a pump can lift a liquid is inversely proportional to its density, but the pump’s head remains constant. .
I agree with the opinions of the two people above. The head of a pump does not refer to the height to which the pump can lift liquid; it is a form of kinetic energy, with that kinetic energy being converted into potential energy. This is the value when drawing water (since the test is conducted with water); when the density changes, it should be recalculated based on that new density.
Head is the energy gained per unit weight of liquid by the pump. It is generally the value at the rated point using water as the medium
To determine how high it can be pumped, one needs to look at the pump’s performance curve; based on general experience, the value is likely around 12.5. Incidentally, head has absolutely no relation to density
May I ask, does \"inverse proportion\" mean that the lower the density, the lower the height it can reach?
Yeah, it doesn’t matter; head is just a property of that kind
In my concept, head is a companion of flow rate; when we transport fluids, what matters actually is the flow rate. For example, if the water volume at the pipe outlet is high, it means the flow rate is high, and if the water pressure at the pipe outlet is high, it means the flow velocity is high. If there is no head loss or frictional loss in the pipeline, then the pump’s output flow rate is very high; at this point, the head actually remains quite low. As the resistance increases, the pump’s flow rate begins to decrease; the energy carried by the reduced flow rate is manifested as head, which is used to counteract the resistance. The head indicated on a pump is generally the rated head.
What was said above is correct: for the same type of pump, head has nothing to do with density, while power is proportional to density.