Questions about pipeline flow rate
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There is a problem at the moment: our company has three circulation pumps for 7-degree chilled water, with a flow rate of 400 m3/h each. These pumps are always in operation, and their outlet pipes are connected together via a DN250 pipe. Logically, the flow rate through a DN250 pipe should also be around 400 m3/h. However, the combined flow rate measured in two of the workshops is approximately 800 m3/h. What’s going on? Could it be that the flow meters in those workshops are broken? I hope someone can help explain this. Thank you
Is the total flow rate of the three pumps 400, or is it 400 for each pump?
Is the total flow rate of your three pumps 400, or is the flow rate of each pump 400?
The flow rate you calculated using DN250 is based on the liquid flow velocity specified by the design institute, and it is not the actual flow rate that the pipeline can transport. If you calculate using a flow rate of 2.5 m/s, that’s the result you get, but in reality, the pipeline can handle a flow rate of 6 m/s.
It’s not clear at all; what the hell is this analysis?
Three ice water transfer pumps supply water to the entire plant’s ice water network. The flow rate of each pump is 400 m3, with a head of 44 meters. The three pumps operate in parallel and are always on; the diameter of the main pipe is DN250. At a flow velocity of 2.5 m/s, the total flow rate through the main pipe is approximately 500 m3. There are two branch pipes leading to the workshops, and the combined flow rate measured by the flow meters in these workshops is 700 m3. I would like to ask whether there is an issue with my calculations or with the flow meters. Thank you
If the medium is water, isn’t the pipe flow velocity usually taken as 0.5–3?
“The pump’s flow rate is 400 m3 – does it really have to be exactly 400 m3? Do you think that just because it’s written on the pump’s nameplate that it will deliver this much flow under any operating conditions? A flow rate of 2.5 meters per second in the main pipe is an economically optimal value chosen during design; it doesn’t mean that all liquids actually flow within this range. In fact, the flow rate delivered by each pump is unknown, and the total flow rate for all three pumps is also unknown. 700 cubic units should be the value actually measured by the flow meter; when the flow meter is used to measure liquid water, the deviation is very small and the readings are fairly reliable. Your calculation doesn’t make sense
The range of values serves as a guide for us in designing the system: it helps us choose a flow rate that results in the most economical operation, while minimizing wear on the pipes and pumps. However, in actual production, situations within the super-flow velocity range are also very common. If the pressure is infinitely high and the pipe can withstand it, the flow rate should also be infinite. It’s better to have no books than to trust them blindly.