Hydro Pipe Sizing

[cvo]

I've a stream fed pond, holding about 12 cubic yards of water.

I've a piece of 8ft 3" PVC pipe beneath the dam and about 3ft. of head below dam.

I'd like to find out if I could reduce the pipe at "X" length to turn a turbine.

The pressure out of the 3" is good about 50gallons per minute.

I checked out Scotty's hydro project...mine is similiar.

I want to maximize the potential and I thought by reducing the 3" to "X" diameter would do the trick.

I need to know if I should even bother or reduce over a given length to a small diameter pipe.

Thanks,

Curtis

[Vtbsr]

How long will the penstock be? The pressure is just a function of the head or vertical drop. You dont want to constrict the flow until you are at the nozzle. If you reduce the dia. of pipe you will just loose the effective head you have.

[scottsAI]

Total head is 6 feet? With 50gal/min.

Not much power, fun to try it out.

6 * 50 / 8 = 37 watts. Less delivered.

Any way to get more flow or more head?

Have fun.

[cvo]

No, there's no other way to get more head or more water.

To get the 6ft. of head I've to run a pipe about 20ft.

Its been fun so far playin in the creek, I've stocked the pond with brown and brook trout....good eating.

Thanks

[scottsAI]

You can build the Banki out of plastic pipe. Cheap and easy.

Scotty's banki is much longer than he needs. By 2x. You have ¼ the flow of Scotty's.

So 3” long turbine should do it. Longer will not hurt anything. Might be easier to build.

Your pip is 20' at 3” should handle the flow without noticeable loss.

Other post have links to flow charts, you should check it just to be sure.

Your nozzle should be <half the area of your pip. Very important.

The nozzles job is to convert PE to KE, the Banki is an impulse turbine.

Your setup will not get you much power, but 25*24 = 600w-hr a day.

Do you plan to build your own generator?

Have fun.

[cvo]

Scott thanks for the info.

Yes, I'm planning on building a generator sized to the output. I'm still learning about how to go about this.

[Nando]

Curtis:

You are defining your problem wrong,

First: One needs to calculate the energy that can be produced with the head and water volume.

3 feet * 0.3048 meter / foot * 50 gallon (minute) / 60 sec * 3.78 liter / gallon * 6 = 17 watts, one may expect a bit LESS due to the frictions and efficiencies at this power level.

Second: One needs to calculate the Turbine ( Banki ?) to optimize its RPM as defined by the generator RPM and its possible direct drive or multiplying "gizmo".

So here is the first step one needs to decide.

Third : for 50 gallon/min or 3 liter/sec with a head of 3 feet= 0.91 meters the Nozzle needs to be defined by the water velocity.

Fourth: Water velocity ( Meter/sec) = squareroot(2*0.91meter*9.81gravity)= 4.22 meter/sec

Fifth: Nozzle calculation: Are of Nozzle = Water volume/water velocity

Area(Nozzle)Cms^2=3000 cms^3/422 cms = 7.1 Cms^2

Sixth: One needs to wait for the Banki diameter to define the Nozzle that should cover 90 degrees of the second quadrant to properly drive the Banki and NOT AS SHOWN IN THIS GROUP IN THE HYDRO SECTION, they are wasting a lot of energy but since NO one there was to pay attention -- that is life.

Seventh: the generator sets the Banki and the final definition of the Nozzle to get maximum power harvesting

So let me know if you want the best system

Regards

Nando