232 posts
TimePosted 07/11/2009 03:00:47
xxxx says

Fan performance curve

IF THE FAN INLET TEM. IS CHANGED FROM 370 TO 230 DEG.

WHAT CHANGES TO BE MADE IN THE FAN CURVE TO CHECK THE PRESENT OPERATING CONDITIONS?

SHOULD I MAKE A CORRECTION FOR VOLUME IN FAN CURVE

OR

ONLY DENSITY CORRECTION TO BE INCORPORATED IN FAN SHAFT POWER & PRESSURE

OR

CHANGE IN DENSITY WRT TEMP. TO BE INCORPORATED IN ALL THAT IS

VOLUME,PR.,KW.

I THINK ONLY CORRECTION IN PRESSURE & KW IS REQUIRED & NO CORRECTION IN VOLUME IS REQUIRED FOR CHANGE IN TEMP. TO DRAW A NEW FAN CURVE WITH NEW TEMP.

RAJESH

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57 posts
TimePosted 10/11/2009 08:29:07

Re: Fan performance curve

The simplified relationships to extrapolate a centrifugal fan (or pump) curve are as follow:

Flow2=Flow1 * (Speed2/Speed1)

Pressure2=Pressure1 * (Speed2/Speed1)^2 * (Density2/Density1)

Power2=Power1 * (Speed2/Speed1)^3 * (Density2/Density1)

Where:

Flow is the fluid volume per unit of time in actual conditions (for example in actual cubic meters per hour and NOT in Normal cubic meters nor in kg/hour)

Pressure is the pressure increase (head) produced by the machine

Speed is the rotational speed of the machine

Density is the density of the fluid (which for a gas is of course heavily depending on the temperature)

These relationships are simplified because they consider that efficiency of the machine is constant.

Best regards