Water Supply & Distribution第 58 / 120 题
Using velocity (fps) = 0.408 x flow (gpm) divided by the square of the inside diameter (in), what is the velocity of 12 gpm flowing in 3/4 in Type L copper with an inside diameter of 0.785 in?
a.About 4.4 fps
b.About 6.0 fps
c.About 7.9 fps
d.About 10.2 fps
解析
0.408 x 12 = 4.896, and 0.785 squared is 0.616, so 4.896 / 0.616 = 7.9 fps, right at the practical 8 fps cold water limit. The 4.4 and 6.0 answers come from dividing by the diameter instead of the diameter squared or from using the nominal 3/4 in size. The 10.2 answer uses a smaller inside diameter such as 0.69 in, which belongs to a heavier wall tube.
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