Design & Sizing第 23 / 110 题
A recirculation loop must deliver 6 gpm of hot water. Using v = 0.408 x Q / d^2, what inside diameter keeps the velocity at about 2 ft/s to limit erosion of the continuously circulated hot line?
a.0.75 in
b.1.50 in
c.1.10 in
d.2.00 in
解析
Solve for d: d = sqrt(0.408 x Q / v) = sqrt(0.408 x 6 / 2) = sqrt(1.224) = 1.11 in. Hot recirculation lines are held to a low velocity, near 2 to 3 ft/s, because constant flow at high velocity erodes copper. A larger diameter lowers velocity for the same flow.
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