What is the relationship between the pressure gauge reading and flow rate?
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The pressure gauge reading on the outlet pipeline is 0.45 Mp, which is equivalent to a pressure of 4.5 Kg. So, isn’t the flow velocity in the pipeline roughly 4.5 m/s? Is there a formula for calculating this?
According to your explanation, basically all flow meters and velocity meters can be discarded. Lower pressure exists in areas with higher flow velocity. According to Bernoulli’s equation, it can also be expressed as p1 + 1/2ρv1² + ρgh1 = p2 + 1/2ρv2² + ρgh2. As a quick reminder, the unit for pressure gauges is MPa, which represents pressure. The kilogram we are talking about is not 4.5 kg; it refers to the pressure exerted by 4.5 kilograms per square centimeter. Pressure is a thermodynamic parameter, while flow rate is a kinematic parameter. These two cannot be directly compared; there is a conversion relationship between them. Of course, in reality it won’t be very accurate, because water does have a certain degree of compressibility. Just trying to get things started – let’s continue downstairs. Bro, I’m packing up; it’s time to leave work!
There is no direct relationship. For the same pipe diameter, higher pressure results in a relatively higher flow rate.
Thank you, sir. Then can the flow rate be calculated only by dividing the flow volume by the cross-sectional area of the pipe?
You can think about it differently. Let’s consider it in terms of units: flow rate is in l/s, which can be converted to m3/s; cross-sectional area is in ㎡, and velocity is in m/s. So m3/s = ㎡ * m/s – does that make sense? Of course, there are many other influencing factors, such as viscosity and roughness. Let’s not consider it that deeply for now. If you think it’s related to pressure, then with the unit of Mpa, how do you eliminate it to get the unit of m3/s? Pressure and flow rate are not in a proportional relationship; the relationship between pressure and flow rate cannot be determined based on factors such as pressure difference, pipe diameter, cross-sectional shape, the presence of bends, pipe wall roughness, whether the pipes have a constant diameter, viscosity properties, and so on. Let me give you another example: when the velocity is 0, the pressure can be infinitely large. This situation occurs when the pipeline valve is closed. I’m being quite straightforward; it’s not as professional or sophisticated as what the experts on forums say, and we try to avoid using technical terms as well. I hope that makes it clear?