Urgent! Need an explanation of how the flow rate changes for pipes of the same diameter under different pressures
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Using the formula F=ma, P=F/S=kg·m/s² ÷ m²=kg/m·s²; however, velocity v is m/s. From this perspective, there is no inherent relationship between the two. Yet in everyday life, it often seems that for the same pipe diameter, the flow rate is higher under a pressure of 10 kilograms than under a pressure of 2 kilograms ? ? ?
The flow rate should be higher when the pressure difference between the front and back is large. Even with a pressure of 10 kg, if you don’t open the valve and hold it back, it won’t flow ； At a pressure of 2 kg, if you release it, for example by venting it, the flow rate can also be adjusted.
So, your understanding is that for the same pipe diameter, the greater the pressure difference, the faster the flow rate? I haven’t been able to find a formula that provides theoretical support for this?
Ideally, there is no resistance in the pipeline; therefore, in the absence of a pressure difference, water, which already has a certain velocity, will continue to move at that speed. However, in real life, there is resistance in pipes; therefore, we need pressure-generating devices such as circulation pumps to create a pressure difference between the fluids, thereby overcoming this resistance and enabling flow. If there is only pressure, as with all circulating water, the water does not flow when the pump is not running. Although the pressure at the bottom is high, there is no pressure difference between the pipes, or the pressure difference is not sufficient to overcome gravity, so the water cannot move. Liquid can flow inside a pipe only when there is a pressure difference. However, it cannot be said that a larger pressure difference necessarily means a higher flow rate; the flow rate is related to pressure loss (such as the roughness of the pipe, the number of bends, the viscosity of the fluid, etc.), the cross-sectional area of the pipe, and the height difference. Other conditions remaining constant, the greater the pressure difference, the greater the flow rate, but it is not proportional.
Can the flow rates differ for a DN100 pipe with a steam medium of 1.0 MPa and a flow rate of 20 m3/h, and one with a steam pressure of 0.2 MPa also at 20 m3/h? The flow rate is of course the same; the pressure is different, but the mass flow rate is not.
Using Newton’s second law for calculations and then determining relationships through units has no scientific basis at all. As for the effect of the pressure difference at both ends of the pipe on the flow velocity, Bernoulli’s equation can be used to determine it
Just look at Bernoulli’s equation and you’ll understand
Pressure energy + kinetic energy + potential energy = CONST. As pressure energy decreases, kinetic energy must increase.
Bernoulli’s equation, ah: victory:
I looked around, but I’m still confused. It would be easier to understand if this were converted into something more common