The gas pipe element is a pipe element with constant cross section (Figure 50).
The friction parameter is determined as
![]() |
(12) |
for laminar flow (
Re) and
![]() |
(13) |
for turbulent flow. Here, is the diameter of the material grains at the surface of the pipe
and Re is the Reynolds number defined by
Re![]() |
(14) |
where is the liquid velocity and
is the kinematic viscosity.
A gas pipe is described
by the following parameters (to be specified in that order on
the line beneath the *FLUID SECTION,TYPE=GAS PIPE
ADIABATIC or *FLUID SECTION,TYPE=GAS PIPE
ISOTHERMAL card):
The default gas pipe is adiabatic, i.e. there is no heat exchange with the pipe. Alternatively, the user may specify that the pipe element is isothermal. This means that the static temperature does not change within the pipe. In that case the energy equation in one of the two corner nodes of the element is replaced by a isothermal condition.
The form factor is only used to modify the friction expression for
noncircular cross sections in the laminar
regime as follows:
![]() |
(15) |
Values for for several cross sections can be found in [10].