7.3.7 Intake Fan Boundary Conditions

Intake fan boundary conditions are used to model an external intake fan with a specified pressure jump, flow direction, and ambient (intake) pressure and temperature.

Inputs at Intake Fan Boundaries

You will enter the following information for an intake fan boundary:

• type of reference frame

• total (stagnation) pressure

• total (stagnation) temperature

• flow direction

• static pressure

• turbulence parameters (for turbulent calculations)

• radiation parameters (for calculations using the P-1 model, the DTRM, the DO model, or the surface-to-surface model)

• chemical species mass or mole fractions (for species calculations)

• mixture fraction and variance (for non-premixed or partially premixed combustion calculations)

• progress variable (for premixed or partially premixed combustion calculations)

• discrete phase boundary conditions (for discrete phase calculations)

• multiphase boundary conditions (for general multiphase calculations)

• pressure jump

• open channel flow parameters (for open channel flow calculations using the VOF multiphase model)

All values are entered in the Intake Fan dialog box (shown in Figure  7.3.6), which is opened from the Boundary Conditions task page (as described in Section  7.1.4).

The first 12 items listed above are specified in the same way that they are specified at pressure inlet boundaries. See Section  7.3.3 for details. Specification of the pressure jump is described here. Open channel boundary condition inputs are described in Section  24.3.1.

Figure 7.3.6: The Intake Fan Dialog Box

Specifying the Pressure Jump

An intake fan is considered to be infinitely thin, and the discontinuous pressure rise across it is specified as a function of the velocity through the fan. In the case of reversed flow, the fan is treated like an outlet vent with a loss coefficient of unity.

You can define the Pressure-Jump across the fan as a constant, polynomial, piecewise-linear, or piecewise-polynomial function of the normal velocity. The dialog boxes for defining these functions are the same as those used for defining temperature-dependent properties. See Section  8.2 for details.