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Use Compressibility

Check this option if you want Centrix to use compressibility when making selections.

Compressibility (Kp):

When the fan pressure starts to get high the gas is compressed as it passes through the fan. Hence the density is increased and the volume reduced as the gas passes from the inlet to the outlet. This increase in density results in the development of a higher pressure by the fan.

Now because fan volume is always specified at the fan inlet there will be an apparent increase in fan efficiency.

Contrary to some standards Centrix does not increase the volume or power when compressibility is used. Only the pressure is increased providing a more conservative (and logical) application of compressibility. (The volume is reduced by the same amount that the pressure increases so power should not increase).

Compressibility is also affected by the fan efficiency. The lower the fan efficiency the greater temperature rise which in turn lowers the density.

Centrix takes these factors into account when calculating the Kp factor and it becomes apparent that high efficiency fans gain a greater effect than low efficiency fans.