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