Existing methods for fan performance model are mostly based on fan static pressure and fan airflow. However, for typical packaged HVAC units, a non-ideal airflow pattern arises due to the compact arrangement of the interior components, resulting in both the fluctuation of the field fan static pressure and the difficulties of installing the pressure sensors. This paper describes the development of the fan performance greybox model, which relates fan power consumption to fan speed and airflow, both of which are much easier to measure. Several practical field measuring or prediction methods of blower speed for the model implement and validation are proposed. Finally, the model is evaluated in terms of interpolation and extrapolation using the manufacturers’ data and validated with laboratory data. This model can be used to predict the power consumption and fan static pressure, for comparative analysis of fan types, wheel diameters widths and air density, and for fault detection and diagnosing of fan operation.

Units: Dual