AIRFLOW RATE
Defined as the air volume required to be extracted or supplied into a room during a given period of time.
Several methods can be used to calculate the required airflow:
CHOICE OF FAN
The fan selection must take into account parameters such as:
1. Type of premises - industrial, commercial, domestic
2. Nature of the air and its characteristics - clean air, air & dust or grease, special fluid (gases)
3. Nature of the installation - supply and extract, wall fan, roof fan, ducted sys tems, position of the air entries, particu lar conditions
4. Requirements of air flow and pressure drop
5. Acceptable sound level in the room and externally
6. Type of mains supply - single phase, three phase, voltage, frequency Other parameters may be considered for the selection such as dimensions, speed controllable motos, mounting accessories etc.
THE FAN LAWS
These laws enable you to change the aerodynamic parameters:
CONVERSION TABLE
PRESSURE DROP
To obtain airflow in a ducted system it is necessary to overcome the resistance of the system:
- due to friction in the duct lenght
- due to the features of the system (bends, cross-section changes, filters, louvres etc.).
These losses must be calculated accurately to select the correct fan and to give the airflow required
SOUND LEVEL
In the catalogue, the sound level specified in the performance guide is a pressure level generally measured at a distance of 1,5 metres from the inlet for centrigugal fans, and at a distance equal to 3 times the impeller diameter (with a minimum of 1,5 m) for the axial flow fans.
