Pipe, Bend

Figure 116: Bend

A bend (Figure 116) is characterized by head losses $\Delta_1^2 F$ of the form:

$$\Delta_1^2 F = \zeta \frac{\dot{m}^2}{2 g \rho^2 A^2 },$$ (170)

where $\zeta$ is a head loss coefficient depending on the bend angle $\alpha$ and the ratio of the bend radius to the pipe diameter $R/D$, $\dot{m}$ is the mass flow, g is the gravity acceleration and $\rho$ is the liquid density. $A$ is the cross section of the pipe. Values for $\zeta$ can be found in file “liquidpipe.f”.

The following constants have to be specified on the line beneath the *FLUID SECTION, TYPE=PIPE BEND card (internal element label: DLIPIBE):

• $A > 0$
• $R/D \;\;\;(\ge 1)$
• $\alpha \;\;\;($in$\; ^\circ), > 0$
• $\xi \;\;\;(0 \le \xi \le 1)$

$\xi$ denotes the roughness of the pipe: $\xi=0$ applies to an extremely smooth pipe surface, $\xi=1$ to a very rough surface. The gravity acceleration must be specified by a gravity type *DLOAD card defined for the elements at stake. The material characteristic $\rho$ can be defined by a *DENSITY card.

Example files: centheat1, pipe.