Question regarding the parallel operation of centrifugal pumps
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I would like to ask everyone: for two centrifugal pumps with identical parameters, assuming the fluid is water for now, if they are operated in parallel and the flow rate increases, does the total outlet pressure change as well?
When two or more water pumps are connected in series, the flow rate does not change significantly, while the head values add up. When two or more water pumps are connected in parallel, the head of the system remains largely unchanged, but the flow rates add up. The series connection of water pumps is commonly used to pressurize water supply networks, and pressure pumping stations in outdoor water supply networks employ this series connection of pumps. Parallel connection of water pumps is commonly used when a single pump cannot meet the flow requirement, or when using a single pump with an excessively high system flow rate would result in increased operating costs. Parallel operation allows the number of water pumps to be adjusted according to water usage levels and peak demand, thereby reducing operating costs.
Additionally, when using them in series, it is necessary to consider the pressure tolerance of the pumps and the system to prevent overpressure.
After parallel connection, it is not the sum of the original flow rates of the two units, as the characteristic curve of the device changes
I agree with what was said on the fifth floor. It can be understood simply as follows: the series and parallel connection of pumps with identical parameters is similar to the series and parallel connection of batteries of the same model. However, in the case of parallel connection, the diameter of the pipes plays a role, which means that the flow rate is not exactly equal to the sum of the flow rates of the two pumps
The total outlet pressure depends on the sum of three components: the static head, the total frictional loss along the pipeline, and the total local losses. The static head does not change with flow rate, whereas both the total frictional loss and the total local losses increase significantly as the flow rate rises. Therefore, when operating in parallel and the flow rate increases, if there are no changes in the piping system, the total outlet pressure will increase. Of course, if the piping system changes – for example, if a valve that was previously open to half its capacity is now fully open – it’s not certain whether the total pressure will increase.
This post was last edited by lupg on 2019-9-9 at 15:31. 1 person agrees with the view of the user in post 8. 2 Parallel operation is not simply a combination of flow rates; when the characteristics of the pipelines remain unchanged, the flow rate is neither twice as much nor equal to the head generated by a single pump. 3 The outcome of parallel operation is largely influenced by the characteristics of the pipelines, and changing these characteristics will result in different outcomes. 4 A simplified diagram showing the behavior in parallel operation is provided for reference
I strongly agree with and support the views of the person on floor 9. Pictures speak louder than words; it’s clear at a glance
With the piping unchanged, the main pipe pressure will increase.