- Dave wrote:
>

1. I am not promoting my PC software. I had nothing to do with its creation

> I repeat the question, but this time can someone answer it with or

> without promoting their PC software?

and had to download a free evaluation copy for subsequent purchase like

everybody else.

2. The question as you have posed it cannot be answered. It depends on the

friction coefficient, which is a function of the pipe material and its

condition. You have yet to tell us what the pipe is made of.

Regards,

Max Enfield

Planetary Power - Dave,

I normally suggest a pipe sizing rule of thumb to keep the flow

velocity in the range of 3-5 ft/sec or 1-1.5 m/sec. However with such

a short pipe you can usually go higher, but remember you don't have

that much head to start with. If you go much higher in velocity, the

entrance and fitting type losses start to be a bigger factor. As

diameters get larger the pipe roughness (steel vs. concrete vs.

plastic etc.) becomes less of a factor. My first cut rough guestimate

would pick a flow rate around 1500 gpm in a 10" pipe and 2200 gpm or

so in a 12" pipe, but that is very arbitrary and based on my personal

assumptions and biases in trading off head loss vs. pipe size etc.

The link below will let you download the spreadsheet I use for such

things. It runs on Mac or PC as long as you have excel. You'll need to

allow macros as the "Moody Chart" for pipe friction losses is

implemented in some visual basic code. It also has runner sizing

calculations which are irrelevant here.

http://h-hydro.com/pipedp.xls

I've added the pipe & draft tube lengths and heads. The gpm & lps tabs

are independent calculations and I haven't entered your site info in

the lps tab. The fittings and pipe roughness tabs have tables for

various fittings and pipe materials.

Please pay attention to all of your entries, and cross check with

other calculation methods before cutting metal and pouring concrete.

The end answer you are looking for depends on constraints and criteria

that you have not specified to us, but which you'll need to determine

for yourself somehow.

Joe

--- In microhydro@yahoogroups.com, "Dave" <got2flyaway2@y...> wrote:

> I repeat the question, but this time can someone answer it with or

> without promoting their PC software?

> > > Can anybody help me figure how many gallons per minute will

flow

> thru

> > > both a 10 inch and 12 inch penstock that is 22 feet long that

has

> a 6

> > > foot 8 inch head without any turbine? The penstock will have

one

> 90

> > > degree bend and a 3 foot draft tube. I trying to determine what

> size

> > > will be ideal to replace the existing 8.25 inch penstock before

i

> > > size a turbine that sizes the penstock. Thanx

> > >

> >

> > 1.

> > This now the fifth time since October last year that I advise the

> group that

> > SF Pressure Drop 5.0 [available at http://www.pressure-drop.com/%5d

> makes it easy

> > to do any pipe friction/pressure drop calculation imaginable.