.Modelica.Fluid.Fittings.BaseClasses.QuadraticTurbulent.LossFactorData.wallFriction .Modelica.Fluid.Fittings.BaseClasses.QuadraticTurbulent.LossFactorData.wallFrictionFriction in straight pipe with walls of nonuniform roughness (commercial pipes) in the region that does not depend on the Reynolds-number
The loss factors are given for mass flow rates from port_a to port_b as:
turbulent flow (Idelchik 1994, diagram 2-5, p. 117)
zeta = (L/D)/(2*lg(3.7 / Δ))^2, for Re >= 560/Δ
for Re ≥ 560/Δ the loss factor does not depend on the
Reynolds number. For Re ≥ 4000, the flow is turbulent,
but depends both on Δ and slightly on Re.
laminar flow (Idelchik 1994, diagram 2-1, p. 110):
zeta = 64*(L/D)/Re
where
Since the LossFactorData record can only describe loss factors that depend on geometry (but, e.g., not on the Reynolds number), only the region with Re ≥ 560/Δ is described by this data. Still, the turbulent region with the above zeta is defined to start at Re=4000, since otherwise the approximation for Re < 560/Δ is too bad.
The absolute roughness d has usually to be estimated. In [Idelchik 1994, pp. 105-109, Table 2-5; Miller 1990, p. 190, Table 8-1] many examples are given. As a short summary:
| Smooth pipes | Drawn brass, copper, aluminium, glass, etc. | d = 0.0025 mm |
| Steel pipes | New smooth pipes | d = 0.025 mm |
| Mortar lined, average finish | d = 0.1 mm | |
| Heavy rust | d = 1 mm | |
| Concrete pipes | Steel forms, first class workmanship | d = 0.025 mm |
| Steel forms, average workmanship | d = 0.1 mm | |
| Block linings | d = 1 mm |
encapsulated function wallFriction
import Modelica.Fluid.Fittings.BaseClasses.QuadraticTurbulent.LossFactorData;
import Modelica.Fluid.Types.Roughness;
import lg = Modelica.Math.log10;
import SI = Modelica.SIunits;
input SI.Length length "Length of pipe" annotation(
Dialog);
input SI.Diameter diameter "Inner diameter of pipe" annotation(
Dialog);
input Roughness roughness(min = 1e-10) "Absolute roughness of pipe (> 0 required, details see info layer)" annotation(
Dialog);
output LossFactorData data "Pressure loss factors for both flow directions";
end wallFriction;