Oval Equivalent Diameter (Ellipse) The equivalent diameter of a oval duct or tube (ellipse) can be calculated as (Heyt & Diaz) de = 1.55 A0.625 / P0.25 (2) where A = cross-sectional area oval duct (m2, in2) P = perimeter oval duct (m, inches) The cross-sectional area of an oval duct can be expressed as A = a b / 4 π where a = major dimension of the flat oval duct (m, in) b = minor dimension of the flat oval duct (m, in) The perimeter of an oval duct (ellipse) can be approximated to P 2 (1/2 ((a / 2)2 + (b / 2)2))1/2 (2b) ≈ π Oblong Ducts Equivalent diameters of oblong ducts or pipes can be expressed as de = b2 / 4 + a b - b + 2 a - 2 b)0.25 (3) 1.55 (π b2)0.625/(π
Oval Equivalent Diameter (Ellipse) The equivalent diameter of a oval duct or tube (ellipse) can be calculated as (Heyt & Diaz) de = 1.55 A0.625 / P0.25 (2) where A = cross-sectional area oval duct (m2, in2) P = perimeter oval duct (m, inches) The cross-sectional area of an oval duct can be expressed as A = π a b / 4 where a = major dimension of the flat oval duct (m, in) b = minor dimension of the flat oval duct (m, in) The perimeter of an oval duct (ellipse) can be approximated to P ≈ 2 π (1/2 ((a / 2)2 + (b / 2)2))1/2 (2b) Oblong Ducts Equivalent diameters of oblong ducts or pipes can be expressed as de = 1.55 (π b2 / 4 + a b - b2)0.625/(π b + 2 a - 2 b)0.25 (3)
7-hydrulic-diameter.docx