LocalResistance

Description

The component LocalResistance is a model of a flow resistance that represents the local pressure loss, which is typically calculated with the Pressure loss coefficient zeta.

Diameter is used for calculation of flow velocity v.

Values of Pressure loss coefficient can be found in literature, e. g. in I.E. Idelchik, Handbook of Hydraulic Resistance.

In the following tables standard values for the resistance coefficient Zeta are given. It is distinguished between bends (without marked radius of curvature R) and elbows (with considerable radius of curvature R), circular cross-sections are always assumed:

Bend

For bends with distinct radius of curvature R the resistance coefficient Zeta changes depending on the angle of curvature phi according to the formula:

From the first table the values for Zeta _90deg depending on the ratio radius of curvature R to tube diameter d can be taken. The second table specifies values for the factor k depending on the angle of curvature phi (where appropriate interpolation is necessary).

At multiple bends, the following equations can give clues for the calculation of Zeta:

Double bend (two bends arranged semicircular):

Room crooked (two bends arranged angular to each other):

Floor crooked (two bends arranged s-shaped):

Elbow

For bends without marked radius of curvature R, Zeta can be taken out of the following table and/or can be computed by interpolation: