Questions regarding pipeline pressure, flow rate, velocity, and diameter changes
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I don’t have any knowledge in fluid mechanics, and I’m facing some problems now, so I’m seeking advice from those with more experience: The air source is a high-pressure gas cylinder, and valves are used to regulate the pipeline in order to maintain a constant pressure. There is a section in the pipeline where the diameter changes, from thick to thin to thick again. Will the local pressures before and after this diameter change (p_thick – p_thin – p_thick) still vary? Does the flow rate change before and after the diameter change? How will the flow rate change? In actual chemical production, when there is a liquid in the pipelines, is the flow rate generally constant throughout the entire pipeline, while pressure and flow velocity vary?
Your question is a bit unclear; what needs to be understood is the relationship between flow rate, velocity, pressure, and the cross-sectional area of the flow path. I recommend a reference textbook, \"Principles of Chemical Engineering\". There are the explanations you need there; give it a try.
I am currently self-studying the principles of chemical engineering and trying to find answers through this material; I think I could start with the mechanical energy balance equations (I’m not sure if that’s correct?) ), but I’m still confused at the moment
In the book \"Principles of Chemical Engineering\", the chapter on fluid transport covers this topic, including several formulas. It can generally be understood with an intermediate level of physics knowledge from junior high school.
With constant flow rate and reduced resistance, the pressure will change
Okay, I’m reading this chapter right now. Thank you
Simply put, flow rate = velocity * cross-sectional area, that is, Q = VA. When the flow rate remains constant, any change in the cross-sectional area leads to a corresponding change in velocity. A change in the cross-sectional area also results in a change in pressure, as described by equations such as Bernoulli’s equation
In other words, even if the pressure in the pipeline remains constant, the local pressure can still vary； Due to reasons such as pipe resistance, the flow rate decreases as long as the cross-sectional area of the pipe changes ； The flow velocity increases where the cross-sectional area decreases; therefore, it first increases and then decreases, ending up being lower ； I’m not sure if I understand correctly?