How to calculate water flow velocity?
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Is there a relationship between the flow velocity in a circulating water system and the water pressure as well as the pressure difference? In a water system with a constant flow rate and diameter, does a change in water pressure result in a change in flow velocity? Can the water flow rate be calculated based on water pressure?
If the pressure loss of a specific section of pipe and its diameter are known, the flow rate can be calculated. This is done by trial and error with the flow rate until the calculated pressure loss value equals the known value
The flow rate can be calculated using the pressure drop; see the chemical process manual
I don’t think it has anything to do with water pressure; water pressure is a requirement dictated by the manufacturing process, and it is not related to the actual flow rate. The flow rate is related to the pressure difference – these are the working principles of some flow meters
Well, thank you all. I agree to a certain extent with the view that flow rate is related to pressure difference, but what level of pressure difference is needed to ensure an adequate flow rate, for example in cooling systems?
Problems in fluid mechanics are generally complex. Although many calculations are simplified in engineering fluid mechanics, similar calculations require knowledge of certain other conditions in order to apply further simplifications and empirical formulas; for example, whether the liquid surface inside the container is a free surface, the volume of the container, the position and type of the outlet nozzle (extending nozzle, retracting nozzle, converging nozzle, diverging nozzle), and so on. Assuming the current situation is one of constant free flow from a cylindrical outlet (with an infinitely large container surface), here is the most basic formula: V = Cv * √(2gH). Here, V represents the exit flow velocity in m/s; Cv is the flow coefficient (which takes into account head losses), and for a cylindrical outlet, Cv = 0.82. g is the local acceleration due to gravity, in m/s²; H is the vertical distance from the centerline of the outlet to the free surface of the container, in meters
Since you say that the flow rate and the path length remain constant, these two conditions allow us to calculate a constant flow velocity; then why ask how the pressure difference changes?
The flow rate is related to the pressure difference, while the relationship with pressure itself is not very significant.
I think they are all related; the higher the pressure, the faster the flow rate, and the pressure difference is mainly caused by pressure, so it’s possible that they are all connected
Given a constant flow rate and pipe diameter, as well as parameters such as pipe length and the number of fittings, the relationship between pressure and flow velocity can be determined using Bernoulli’s equation.
The flow rate can be calculated using the pressure drop; generally, it can be determined with reference to materials such as chemical process manuals
In short, the pressure difference is proportional to the square of the flow velocity, from which the change in flow velocity resulting from a change in pressure difference can be inferred.
Thank you, I don’t want to know how it’s calculated exactly. I just want to know, given a fixed pipe diameter, what minimum pressure difference is required to ensure a certain flow rate (water supply volume). Thank you in advance
For complex systems like circulating water, is more reliance placed on experience or precedents? Please ask an expert to answer
Baidu has relevant calculation software; you can give it a try
We need to analyze each case on its own; for some, we can make judgments based on experience