What determines the flow velocity of different media in pipes?
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What determines the flow velocity of different media in pipes? How is the recommended flow rate determined? For example, what are the hazards of exceeding or falling below this flow rate? Does this flow rate have nothing to do with the specific material of the pipe?
You can look at some books that discuss fluid flow rates. Basically, they are divided into liquids and gases. The flow rate of liquids is usually around 2–3 M/S, while that of gases is 20–30 M/S (in industrial applications, the flow rate for liquids is 1–2 M/S, and for gases it’s 35–40 M/S). This has nothing to do with the material of the pipes. As for why there are limits, it’s mainly because too slow a flow rate can lead to sedimentation, while too fast a flow rate can cause erosion. Of course, factors such as viscosity and the presence of particles need to be considered as well. The above is based on personal experience
Too high a flow rate results in high pipeline resistance and increased energy consumption; it also causes frictional damage to the pipes. If the flow rate is too low, it is necessary to use larger pipes, which increases costs. Larger pipes require larger valves as well, making it difficult to maintain a stable flow rate; moreover, a low flow rate can lead to sedimentation. It’s too slow; it’s difficult to match with a pump. Using a large pump for a low flow rate results in high energy consumption and also damages the pump
I think there must be a connection – different materials have varying levels of smoothness, which in turn results in different resistances; thus, the loss of kinetic energy also varies. What I don’t understand is how the loss of kinetic energy at the outlet is related to the speed and resistance
This post was last edited by Yimeng on 2018-11-16 at 11:25. In Table 2.0.1 of HG20570.6-95, there are many flow rates for commonly used medium pipes. Generally, the flow rate of flammable and explosive gases is lower than that of steam, air, etc., as these gases are prone to leakage due to static electricity or pipe erosion. . . I’ve encountered situations where, in an attempt to increase production, the flow rate of CO+H2 was raised, which led to erosion and leakage at the pipe bends, and subsequently a fire broke out. . . In principle, things that are dangerous are slower than those that are not; for example, hydrochloric acid and water – hydrochloric acid is definitely slower. Once the process requirements are met, slower is safer. Then select the material based on the flow rate.
Basically, the flow rate has nothing to do with the choice of material, because when the fluid flows too fast, erosion/corrosion will occur in any metal. The key to selecting a material lies in considering the properties of the fluid itself (such as its corrosive capacity at different concentrations and temperatures)
The material doesn’t matter, unless you require a certain level of polishing... But how can the inside of pipes be polished?? Basically, if you deliberately polish it, the thickness will decrease, which may lead to corrosion. Moreover, bends in the pipes themselves create friction; it’s better to reduce pressure loss in the pipes through proper design. -------------------------- As for kinetic energy loss versus flow rate versus resistance... the greater the resistance, the greater the kinetic energy loss. The flow rate isn’t necessarily proportional to kinetic energy loss (in some cases, the equipment is too high and the pump’s head isn’t sufficient... so the flow rate is low)