Water acts the same going straight up as it does coming straight down, only in reverse. If you want to know the max height water will shoot up to from a sprinkler with the deflector removed, the fastest is: h=PSI/.433. If you like seeing the velocity when imagining flowing water: v=(SQRT)2gh. If you want to know the time required to reach max height: t=v/g If you want to use gravity and time: h=.5g*t^2 Using velocity and gravity: h=v^2/2g.
In the formula Q=K*(SQRT)P atmospheric pressure and air friction are neglected. I believe this is because water is 780 times 'stronger' than air. Rocci, does the AHJ think rack sprinklers will never activate either, being so far down from the roof deck, with no heat collector? thanks, Brad Casterline AFSA Designer Member and SET -----Original Message----- From: Sprinklerforum [mailto:[email protected]] On Behalf Of å... .... Sent: Tuesday, July 07, 2015 6:53 AM To: [email protected] Subject: Re: Column Protection We can use the sprinkler nozzle pressure, but as a means to the end of estimating how high the sprinkler will project water: 1. use the nozzle pressure with K-factor to get flow = Q, 2. with Q, divide by sprinkler orifice area (A) to get velocity. This is the max possible velocity as deflector will slow 90% of the spray. 3. from velocity, use Bernoullis at v2= 0 m/s velocity, to predict the height water will rise 4. note, once the water is outside the sprinkler, the pressure is essentially ambient, so P1 ~ P2 in Bernoulli's equation. 5. solve for z, maximum height the water will rise from vertically oriented sprinkler. This seems like a lot of energy and discussion for a relatively minor sprinkler design point. I mean, if we have gotten to the point of a fire where a column sprinkler is to save the structure, perhaps we earlier missed some more important fire protectioin design-issues, at least more important than sidewall horiztonal or sidewall down/up. Do you think sometimes we put more energy into debating the simple points, because they are simpler to think about, and we spend less time debating the not-so-clear subject material, because we don't want to spend the mental energy, even though that is the effort that would yield the-most-design value for the time? Scot Deal Excelsior Fire/Risk Engineering _______________________________________________ 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
