where Pr = μCp ⁄ k,
ReD = ρUextD ⁄ μ and
n = 0.3 if
T < Text and
n = 0.4 if
T ≥ Text.
D (the tube diameter) and the velocity
U are correlation inputs. All material data are evaluated at
(T + Text) ⁄ 2 except
μs, which is evaluated at the wall temperature,
T.
