Equation Needed for Calculating Fluid Pressure In a Pipe

In summary, a friend is planning to use a local stream to generate electric power. The source of the stream is a small pond and the plan is to have a 5 inch pipe start at the bottom of the pond and run approximately 1056 feet to a culvert where a generator will be placed. The drop in elevation is about 40 feet and the pipe will be closed with no air. Towards the end, the pipe diameter will be reduced, causing an increase in velocity and requiring the use of Bernoulli's equation to calculate pressure. However, before reaching that point, the pressure at the end of the pipe must be determined. A Google search for "40 feet head to psi" yielded the answer of 17.32
  • #1
RobertJBaker
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A friend is planning to utilize a local stream to create electric power. The source of the stream is a small pond. He plans to have a 5 inch pipe start at/near the bottom of the pond and this pipe will follow the stream approximately 1056 feet to a culvert where he wants to put the generator. The drop in elevation is about 40 feet. The pipe will obviously be closed and have no air. Towards the end, the pipe diameter will be reduced, and I know that the velocity will increase and I'll need to use bernoulli's equation but before we even get to that point I need to know how much pressure will be coming out at the end of that pipe and I haven't been able to find an appropriate equation or method of getting there.
 
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  • #2
:welcome:

I just googled "40 feet head to psi" and it gave me the answer 17.32 psi.

That will be the pressure at zero flow. From that you must subtract the pressure drop due to friction. Google "friction loss pipe calculator.

With such a long pipe, the inertia will be a significant factor. If you shut the valve suddenly at the generator end, the pressure will surge and it could burst the pipe. Shut a valve suddenly at the pond end could implode the pipe.

The key to all such calculations is the flow rate and the power generation.

How much water flow is expected?

How much power do you need to generate to declare it a success?

Another Google search, "DIY hydro generator" returned 6360 hits. With a little bit of study, you can learn much from those who have gone before.

Good luck.
 

Related to Equation Needed for Calculating Fluid Pressure In a Pipe

1. What is the equation for calculating fluid pressure in a pipe?

The equation for calculating fluid pressure in a pipe is P = ρgh, where P is the pressure, ρ is the density of the fluid, g is the acceleration due to gravity, and h is the height of the fluid column.

2. How is the equation for fluid pressure derived?

The equation for fluid pressure is derived from the fundamental principles of fluid mechanics, including Pascal's law which states that pressure in a fluid is transmitted equally in all directions, and the hydrostatic equation which relates pressure to the height of a fluid column.

3. What are the units of the variables in the fluid pressure equation?

The units of the variables in the fluid pressure equation are Pascals (Pa) for pressure, kilograms per cubic meter (kg/m3) for density, meters per second squared (m/s2) for acceleration due to gravity, and meters (m) for height.

4. Can the fluid pressure equation be used for any type of fluid?

Yes, the fluid pressure equation can be used for any type of fluid, as long as the density and acceleration due to gravity are known. However, it is important to note that the equation may not accurately predict the behavior of non-Newtonian fluids, such as blood or ketchup, which do not follow the simple rules of fluid mechanics.

5. How can the fluid pressure equation be applied in real-world situations?

The fluid pressure equation can be applied in many real-world situations, such as calculating the pressure in a water pipe, determining the force exerted by a liquid on a dam, or predicting the depth at which a submarine can safely dive. It is an important tool for engineers, physicists, and other scientists working with fluids.

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