>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
