Flow rate when centrifugal pumps are used in parallel
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Dear teachers, I have a question: There are two centrifugal pumps with a flow rate of 1200 cubic meters per hour and a head of 70 meters (with an outlet diameter of 250 mm), and two pumps with a flow rate of 700 cubic meters per hour and a head of 70 meters (with an outlet diameter of 200 mm). These four pumps are connected in parallel to a pipeline with a diameter of 500 mm. What would be the approximate total flow rate when they are connected in parallel?
Flow is distributed according to head; it is less than the flow when operating alone
This post was last edited by ztxfhl on 2018-2-12 at 19:46. No one can answer the question you raised. You specified that the flow rate and head of the 4 pumps are their rated values; in actual operation, these values are not the same in most cases. To determine flow rate and head from the pump’s characteristic curve, it is necessary to have the pipe resistance characteristic curve. The intersection point of each pump’s flow-head curve with the pipe resistance characteristic curve represents the actual flow rate for that pump; the sum of the actual flow rates of the four pumps gives the total flow rate.
For a pipeline of 500, the flow rates corresponding to speeds of 2 m/s and 3 m/s are 1413 cubic meters per hour and 2120 cubic meters per hour respectively. The combined flow rate of two centrifugal pumps with a flow rate of 1200 cubic meters per hour each is 2400 cubic meters per hour; therefore, the pipeline used for connecting these four pumps must be quite narrow. Generally speaking, the total flow rate will be significantly higher than the sum of the individual flow rates of the four pumps.
I have a question: How can the pipe resistance characteristic curve be obtained?