Pipe Bend (IL)

The coefficient of local resistance (pressure loss) of the curved section of the channel includes a correction factor for the angle of rotation of the channel and the channel bending coefficient :

In the coefficient block calculated as follows:

where — the angle of rotation of the channel in degrees, the value of the parameter Bend angle.

Ratio It is calculated on the basis of experimental data – a table of the dependence of the desired coefficient on the ratio of the bending radius. to the pipe diameter for channel rotation angles 90° according to [1]:

Coefficient of friction It is interpolated based on tabular data taken for technical steels, depending on the pipe diameter [1]. The table below shows the data for the coefficient of friction of a fluid flow with developed turbulence in pipes made of technical steels.

The correction factor of the channel rotation angle is valid for curved pipes (channels) in which the ratio of the bending radius to the pipe diameter ranges from 1 before 24. Outside of this range, nearest neighbor extrapolation is used.

The pressure loss expressions are the same for the flows in ports A and B.

In the case of a laminar flow regime in a pipe bend, or when the Reynolds number is below the critical value , the pressure loss at the bend of the pipe is determined as follows:

where

For flows with developed turbulence, or if the Reynolds number exceeds the critical value , the pressure loss in the pipe bend is determined as follows:

where — Darcy’s coefficient of friction. It is approximated by the empirical Haaland equation and is determined by the absolute roughness of the inner surface (the value of the parameter Internal surface absolute roughness). The pressure drop is taken in half of the pipe section, between port A and the inner node, as well as between the inner node and port B.

In the case of an incompressible fluid, the pressure loss at the bend of the pipe is determined as follows:

In the case of a compressible fluid, the pressure inside the curved pipe is also taken into account when calculating the pressure loss at the bend. :

In the case of an incompressible fluid, the mass flow rate through the block is maintained.:

In the case of a compressible liquid, the difference in flow rates at the inlet and outlet of the block is determined by the change in the density of the liquid inside the curved section of the pipe (pipe bend):

where — the volume of the curved section of the pipe (pipe bend), which is defined as the product of the cross-sectional area of the pipe and the length of the bend, .