I would strongly caution against using this method for estimate calculations. (Without doing extensive testing to verify that it is accurate)
The D-W and H-W calculation methods are simply approximations of how fluids interact with themselves and the pipe they are in. The H-W equation and the K-factor concept are two VERY specialized cases that are intended only to describe warm water in pipes coming out of a smooth hole. The k-factor only relates the ease with which water can escape a sprinkler. If you plug in a modified k-factor, you are still using H-W to describe how the fluid is moving through the pipes. The reason that you have to switch to the D-W equation is because H-W will give you the wrong answer. If you use a modified K factor with H-W (instead of D-W) the most likely outcome is a wrong answer - although maybe not the same wrong answer as before. Matt Grisé PE*, LEED AP, NICET II Sales Engineer Alliance Fire Protection 130 w 9th Ave. North Kansas City, MO 64116 *Licensed in KS & MO 913.888.0647 ph 913.888.0618 f 913.927.0222 cell www. AFPsprink.com On Jun 11, 2013, at 7:52 AM, "Brad Casterline" <[email protected]> wrote: > From NFPA 13-2007, 22.4.4.5.1, we are required to, among other things, > adjust the K-Factor. > > Using the Hazen-Williams friction formula, 62.4 lb/ft3 / 144 in2 = .433 > lb/in2/ft(h). > > If we have an AF solution at 65.5 lb/ft3, / 144 = .455 lb/in2/ft(h). > > If K=5.6, and we assume P=7 PSI.: > > 7/.433=16.166 ft(h). 7/.455=15.385 ft(h).* > > 15.385/16.166=.952. sqrt(.952)=.976, x 5.6 = 5.46. > > There is a chart in 13 showing a 50% glycerin solution at about -10F > weighing about 15% more than 100% water: 62.4 x 1.15 = 71.76. > 71.76/144=.498. 7/.498=14.056 ft(h). 14.056/16.166=.869. sqrt(.869)=.932, x > 5.6 = 5.22. > > If I had to fab the pipe today and formalize the submittal tomorrow (after > googling centipoises for several hours) I would calc it like it was 'all > wet', using K=5.22. > > * converting PSI to feet of head(h) it is seen that the denser the solution, > the 'shorter' it is. Since v=sqrt(2gh), the shorter it is the slower it is. > Making the adjustment based on "h", we have to take the square root of the > ratio, i.e., (K=Q/sqrtP). If adjusted based on velocity we would use the > ratio itself (square feet=cubic feet per second divided by feet per second): > sqrt(2*32.2*16.166)=32.266 ft/sec. > > sqrt(2*32.2*15.385)=31.477 ft/sec. > > 31.477/32.266=.976. > > > > The above is simply the type of thing I enjoy doing and like to share, > hoping it will cause no harm, to be taken or left as one sees fit. > > > > thanks, > > > > Brad Casterline, NICET IV > > Fire Protection Division > > > > FSC, Inc. > > P: 913-722-3473 > > [email protected] > > www.fsc-inc.com > > > > Engineering Solutions for the Built Environment > > > > _______________________________________________ > Sprinklerforum mailing list > [email protected] > http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org
