Hydraulic diameter
Hydraulic diameter Dh = 4A/S for a rectangular duct (sides a, b) and, independently, for the annular gap between two concentric round tubes (outer/inner diameter).
Cross section, A (rectangular)200
Wetted perimeter, S (rectangular)60
Hydraulic diameter, Dh (rectangular)13.333333333333334
Cross section, A (annulus)58.90486225480862
Wetted perimeter, S (annulus)47.12388980384689
Hydraulic diameter, Dh (annulus)5
Two independent legacy sub-calculators (rectangular duct via solve1, concentric-tube annulus via solve2) are combined into one module since neither depends on the other's inputs. No unit conversion and no rounding are applied anywhere, matching the original exactly (the legacy source writes raw, unrounded values to the form).
Method & references
- Hydraulic diameter Dh = 4A/S for non-circular ducts, applied to a rectangular groove and to a concentric-tube annulus.
The computation is a literal port of the original client-side JavaScript from /calculators/hydraulic_diameter.htm. Results are verified equal to the original by an automated golden-master test. No formula has been re-derived or “improved”.