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### Gas Pipe (Fanno)

The gas pipe element of type Fanno is a pipe element with constant cross section (Figure 79), for which the Fanno formulae are applied [71].

It is described by the following parameters (to be specified in that order on the line beneath the *FLUID SECTION,TYPE=GAS PIPE FANNO ADIABATIC or *FLUID SECTION,TYPE=GAS PIPE FANNO ISOTHERMAL card):

- A: cross section of the pipe
- D: diameter of the pipe
- L: length of the pipe
- : grain diameter at the pipe surface
- form factor
- oil mass flow in the pipe (only if the OIL parameter is used to define the kind of oil in the *FLUID SECTION 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 non-circular cross sections in the laminar regime as follows:

| (16)

Values for for several cross sections can be found in [13].

Example files: gaspipe-fanno10, gaspipe-fanno8-oil.

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