What are Fan Laws?!!
Fan Affinity Laws ( Fan laws ) come in handy when one is trying to figure out how the performance of a fan is going to vary upon changing the variables under which a fan operates.
CAUTION: These laws can only be adopted for fans that have the same rating on the fan performance curve and are geometrically similar.
Name, Title
VARIABLES INVOVLED
Q - Airflow (Volumetric Flow) Rate
P - Pressure built by the fan
N - Rotational Speed of the fan wheel
W - Power input of the fan
D - Fan Diameter (or fan size in case of geometrically similar fans)
ρ - Density of air
This law is of assistance when we are trying to examine how the following variables are affected when we change the wheel rotational speed (N), air density (ρ) or fan diameter (D).
(i) FLOW
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(ii) PRESSURE
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(iii) POWER INPUT
FAN LAW 1
This law is of assistance when we are trying to examine how the following variables are affected when we change the pressure built by the fan (P), air density (ρ) or fan diameter (D).
(i) FLOW
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​
(ii) ROTATIONAL SPEED
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​
(iii) POWER INPUT
FAN LAW 2
This law is of assistance when we are trying to examine how the following variables are affected when we change the volumetric flow rate (Q), air density (ρ) or fan diameter (D).
(i) ROTATIONAL SPEED
​
​
(ii) PRESSURE
​
​
(iii) POWER INPUT
