This model represents a fan in a circuit system. The characteristic of the fan is defined with the nominal operating point. The nominal mass flow rate m_flowNom, and the nominal power PNom, of the fan are defined at nominal fan speed wNom. The nominal mass flow rate of the medium is related to the fan speed according to a linear function. The dependence of the mass flow rate on the fan speed is represented in figure 1. The mass flow represents the mass flow rate characteristic of the fan and the marked OP indicates the nominal operating point of the fan.

Figure 1: Relation between the mass flow rate and the fan speed.

The nominal power of the fan is modeled with a cubic function, which is related to the fan speed. The dependence of the power on the fan speed is represented in figure 2. The curve power represents the power of the fan and the mark OP indicates the nominal operating point of the fan.

Figure 2: Dependence of the power of a fan on the fan speed

Boundary condition

If the model of the fan is operated then the mass flow rate is strictly defined by the operating curve. The mass flow rate of the fan is not dependent on the pressure loss in a pipeline or a circuit. The mechanical losses of the bearings of the fan are not considered. The fan can be driven in positive and negative speed direction whereas the mass flow and power characteristic in both directions have the same absolute value.