Calculating Water Flow at 25mph: A Pool Design Challenge

[monze5]

does anyone know how i could go about calculating how much power is needed to move 1,972,080 gallons of water at a constant rate of 25mph or 475,200,000 ft/s?...my friend and i are trying to figure out how to draw up a pool of water that would do this and i don't know how i could go about solving that...the dimensions of the pool are 120x110x20 ft ergo giving the gallons of water i stated above. thank you for your time.

 

[berkeman]

does anyone know how i could go about calculating how much power is needed to move 1,972,080 gallons of water at a constant rate of 25mph or 475,200,000 ft/s?...my friend and i are trying to figure out how to draw up a pool of water that would do this and i don't know how i could go about solving that...the dimensions of the pool are 120x110x20 ft ergo giving the gallons of water i stated above. thank you for your time.

Well, 25mph isn't 475,200,000 ft/sec. That second speed is probably a typo.

The power required is related to the height that you need to raise the water, and to the resistance of the pipes you use to move it (and to the efficiency of the pump). It takes close to zero energy if you want to move it to a lower point, and can just prime a hose or pipe to start it flowing. To get 25mph, you'll need a pretty good head (height).

Are you pumping it to the same or higher level, or can you use gravity to help out? What pump technology do you want to use?

 

[FredGarvin]

It's also going to depend on the hose size and distance away you want to pump the water. Are you going to use a standard type of submersible pump with about a 2 inch diameter flex hose? I am making the assumption that both reservoirs are at atmospheric pressure.

 

[monze5]

Originally it was going to be a horizontal surface, but now that i know that it would be a lot easier using one with a negative slope we can use that. I don't know anything about pumps, the buddy I am working with to draw it up is the mechanical guy. Any suggestions?

 

[berkeman]

Originally it was going to be a horizontal surface, but now that i know that it would be a lot easier using one with a negative slope we can use that. I don't know anything about pumps, the buddy I am working with to draw it up is the mechanical guy. Any suggestions?

Why the 25mph requirement? It would be more traditional to talk in terms of liters per second or some other volume/time measure. Pumps probably come rated in that kind of measure, and then you just need to be sure to use a big enough pipe that you don't introduce too much drag.

 

[FredGarvin]

I think without knowing exactly what you are doing, I will just recommend a rule of thumb until you can be more specific with what it is you are doing.

A general industry rule for water is:

$$HP = \frac{Q*H}{3960}$$ where:

HP = power to raise water in horsepower
Q = flowrate in gal/min
H = total head in ft.

You'll have to adjust the size of the pipe you are using to accommodate the velocity of 25 mi/hr (36.7 ft/sec) you desire by using the relation of $$Q = V*A$$ where:

Q = flow rate (don't forget to use the right units!)
V = velocity in pipe (using the proper units!)
A = area of the pipe (again, use the proper units!)

So, using your velocity desired and area of the pipe you can use, calculate the required flowrate (Q) of the pump you will need. Then from there you can calculate the HP required considering the total head created by the piping in your system.

 

[young e.]

Take Fred Garvins Advice!

 

[Artman]

I think it's been mentioned, but you are missing some parameters. How much water you want to move at 25 mph. This is a function of the size of the pipe it is moving through, as FredGarvin said. and the height difference from the water's start to finish, as berkman said.

The HP to raise the water can be varied some by changing pipe size and reducing or adding friction, but the height is a constant value and will need to be your starting point with pipe losses for the entire system (suction and discharge) added to that. As a real world project, the energy required to move this water can vary with efficiency of the pumping system. For instance, if you don't mind wasting water and you have the proper conditions, a ram pump can move a reduced percentage of the water at a cost of wasted water, but no external power, very inefficient pump, but great if external power (other than the potential energy in the height of the water) is just not near.

 

[Gokul43201]

monze, please provide a diagram or a complete desciption of the problem. There's not enough information right now. For instance, at the very least, one must know how far away from the pool the water wants to go and how big the pipe is (and what it's made of). Also, at what height relative to say, the top of the pool, is the far end of the pipe ?