Hello,
Looking for clarification on how fans work, theory vs real life.
I am told that if one measures the volumetric flow rate through a system it will be the same at all other conditions. So for a given electronic box and fan that flows 50 CFM of air at STP it will also flow 50 CFM at 50°C-SeaLevel. The only thing that changes is the mass flow rate.
When looking at the fan alone, specifically the fan curve with volumetric flow rate versus static pressure, one can compensate for changes in density by scaling the operating pressure. Generally speaking:
Static-Pressure_Actual = Static-Pressure_Standard * (Density_Actual / Density_Standard)
Similarly, I believe the box impedance curve can be scaled using the same equation. Although this may not be true.
The following is a screen-shot from a spreadsheet that performs the above scaling and calculates the curve intercept points.
What is of interest is the fact that the two points do not occur at the same volumetric flow rate. So is the above spreadsheet incorrect? Do I need to force the two operating points to occur at the same flow rate?
Thanks in advance.
Looking for clarification on how fans work, theory vs real life.
I am told that if one measures the volumetric flow rate through a system it will be the same at all other conditions. So for a given electronic box and fan that flows 50 CFM of air at STP it will also flow 50 CFM at 50°C-SeaLevel. The only thing that changes is the mass flow rate.
When looking at the fan alone, specifically the fan curve with volumetric flow rate versus static pressure, one can compensate for changes in density by scaling the operating pressure. Generally speaking:
Static-Pressure_Actual = Static-Pressure_Standard * (Density_Actual / Density_Standard)
Similarly, I believe the box impedance curve can be scaled using the same equation. Although this may not be true.
The following is a screen-shot from a spreadsheet that performs the above scaling and calculates the curve intercept points.
What is of interest is the fact that the two points do not occur at the same volumetric flow rate. So is the above spreadsheet incorrect? Do I need to force the two operating points to occur at the same flow rate?
Thanks in advance.
