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 [EMAIL PROTECTED], "Dave" <[EMAIL PROTECTED]> 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/] > makes it easy > > to do any pipe friction/pressure drop calculation imaginable. ------------------------ Yahoo! Groups Sponsor --------------------~--> Yahoo! Domains - Claim yours for only $14.70 http://us.click.yahoo.com/Z1wmxD/DREIAA/yQLSAA/FGYolB/TM --------------------------------------------------------------------~-> Does your company feature in the microhydro business directory at http://microhydropower.net/directory ? If not, please register free of charge and be exposed to the microhydro community world wide! NOTE: The advertisements in this email are added by Yahoogroups who provides us with free email group services. The microhydro-group does not endorse products or support the advertisements in any way. More information on micro hydropower at http://microhydropower.net To unsubscribe: send empty message to [EMAIL PROTECTED] Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/microhydro/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
