Subject to the only alteration to the ventilation system being alteration of the fan speed within its designed perameters:
Volume varies directly as speed. Pressure varies as the square of the speed. Power varies as the cube of the speed.
Doesn't it get a bit more complicated than that? I thought the shape of the fan blades affected the performance curve significantly.
Chris
As you imply, I had believed power was between a square and cube of speed, much like air resistance of moving objects like cars.
Are you suggesting that fixed fan blades morph to a different shape in use? I am aware that attack angle of some duct type propellor aerofoil fan blades can be changed (whilst in motion? - not sure). This type of fan usually has a characteristic curve for each attack angle. Different centrifugal fan types (forward curve, backward curve, paddle blade,etc., and configurations inbetween) have impellor profiles suitable for its proposed use and each has its own unique characteristic curve but all still obey the fan laws.
My statement referred to the effect of speed change only without any other change to the installed system. I am not suggesting that an upward speed change beyond the fan design parameters and/or system parameters is desirable or safe.
To update this, we didn't actually get a formal response from the said consultant. Instead we were just told to proceed because it 'won't be a problem'!!!
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