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Anika

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In summary, to calculate the flow rate of water in a 4inch pipe at the start of the pipe with a pressure of 4 bar, you will need to consider the downstream pressure and the type of liquid flowing within the pipe. You can use the Bernoulli equation to factor in friction and elevation changes, and the Darcy Weisbach equation to determine the flow rate based on the configuration of your system and the amount of water that needs to be discharged.

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Anika

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SteamKing

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Anika

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SteamKing

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Look, you could take an isolated pipe and pressurize it to 4 bar. There would be no flow, but the pressure inside the pipe would still be 4 bar.

If you are not familiar with the Bernoulli equation, perhaps this will help:

http://www.princeton.edu/~asmits/Bicycle_web/Bernoulli.html

Because this is water in a pipe, there will be friction, which the Bernoulli equation can be modified to include.

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Travis_King

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Unless the water is flowing into a pressurized container, it will have to discharge at atmospheric pressure. This means that between the water main (@ 4bar gage) and the outlet (atm), the liquid will have to lose 4 bar of pressure. It can lose the pressure in two ways. Losses due to static pressure loss from elevation change (outlet is higher in elevation than inlet) and dynamic pressure losses due to friction (from the water flowing through the pipe, through valves, filters, etc).

You can easily determine the static loss expected by looking at the elevation difference between inlet and outlet.

The friction loss calculation is a bit more involved, but basically: a pipe of a given material will experience a certain amount of non-reversible energy loss (realized by reduced pressure) for a given flow rate. This is true of fittings, valves, filters, elbows, etc. It's a balancing act. More flow means more pressure loss per foot of pipe. Less flow means less losses. Your flow rate is determined by the configuration of your system and how much water needs to flow through your pipes in order dissipate enough energy that the liquid leaves the system at atmospheric pressure.

Check out the Darcy Weisbach equation and all the stuff that goes along with it: http://www.engineeringtoolbox.com/darcy-weisbach-equation-d_646.html

The pressure and flow in a pipeline are directly related. As the pressure increases, the flow rate also increases. Conversely, as the pressure decreases, the flow rate decreases. This is known as the Bernoulli's Principle, which states that an increase in the speed of a fluid results in a decrease in its pressure, and vice versa.

Pressure in a pipeline is typically measured using a device called a pressure gauge. This gauge converts the pressure into a readable measurement, such as pounds per square inch (psi) or kilopascals (kPa). Other methods of measuring pressure include using manometers or pressure transducers.

There are several factors that can affect the pressure and flow in a pipeline. These include the diameter and length of the pipeline, the viscosity of the fluid being transported, and any obstructions or bends in the pipeline. Changes in temperature, altitude, and the type of pump used can also impact pressure and flow.

The pressure in a pipeline can be calculated using the formula P = F/A, where P is pressure, F is force, and A is the cross-sectional area of the pipeline. The flow rate can be calculated using the formula Q = AV, where Q is flow rate, A is the cross-sectional area, and V is the velocity of the fluid.

There are various ways to control pressure and flow in a pipeline, depending on the specific needs and constraints of the system. These methods include using pressure regulators, flow control valves, and pumps with variable speed drives. Properly sizing and designing the pipeline can also help to maintain desired pressure and flow rates.

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