Feet Per SecondDate: 02/22/2003 at 15:10:12 From: Steve Subject: Formula To determine the velocity in a pipe in ft. per second: Velocity = gpm x 0.3208 ___________________ A Where: A is area of pipe in sq. inches, gpm is gallons per minute (US) In regards to this formula, how does the numerical figure 0.3028 apply (where does this figure originate)? Date: 02/23/2003 at 09:19:12 From: Doctor Jeremiah Subject: Re: Formula Hi Steve, One gallon is 231 cubic inches, so: in^3 = gal x 231 in^3/gal in^3/min = gal/min x 231 in^3/gal A in^2 x in/min = gal/min x 231 in^3/gal Which gives us an equation of: in/min = gal/min x 231 in^3/gal ---------------------- A in^2 But we aren't looking for inches per minute. We are looking for feet per second. in/min = ft/sec x in/ft x sec/min in/min = ft/sec x 12 in/ft x 60 sec/min ft/sec = in/min / (12 in/ft x 60 sec/min) So, if we divide both sides of the equation by 12x60 we will end up with feet per second: in/min = gal/min x 231 in^3/gal ---------------------- A in^2 in/min gal/min 231 in^3/gal --------------------- = ------- x --------------------- 12 in/ft x 60 sec/min A in^2 12 in/ft x 60 sec/min gal/min 231 in^3/gal ft/sec = ------- x --------------------- A in^2 12 in/ft x 60 sec/min But 231/(12x60) = 0.32083 so the formula can be written as: gal/min ft/sec = ------- x 0.32083 A in^2 Which is the same as the formula you wrote. - Doctor Jeremiah, The Math Forum http://mathforum.org/dr.math/ |
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