Exhaust fans always expel fluid from the cabinet. The flow exits the cabinet in a direction perpendicular to the fan. You can not change the flow direction of exhaust fans.
For intake fans, the flow direction can be normal or along a specified vector to the plane of the fan. If the flow direction is normal to the fan, the direction of flow is always into the cabinet regardless of the fan location. If the flow direction is specified by a vector, the flow direction is fixed by the specified vector. When the flow direction is specified by a vector, the direction vector must properly specified such that the flow direction is into the cabinet. For example, if the fan is located at the maximum x plane of the cabinet, the x component of the flow direction must point in the negative x-axis direction. See Figure 21.6: Intake Fan Flow Direction.
Internal fans can be located anywhere inside the cabinet. Fluid flows through the fan in a direction perpendicular to it. You must specify the direction of flow (positive or negative) for an internal fan. For a rectangular, 2D polygon, or circular fan, if flow is in the direction of increasing axis coordinates, the inward direction is positive. If flow is in the direction of decreasing coordinates, the inward direction is negative. For an inclined fan, the positive and negative directions are defined with respect to the axis of rotation for the inclined fan:
If the axis of rotation of the inclined fan is the x axis, the positive inward direction is the positive y direction, and the negative inward direction is the negative y direction.
If the axis of rotation of the inclined fan is the y axis, the positive inward direction is the positive z direction, and the negative inward direction is the negative z direction.
If the axis of rotation of the inclined fan is the z axis, the positive inward direction is the positive x direction, and the negative inward direction is the negative x direction.