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A ventilator fan mounted on the wall of an air tight room(except for an air intake with a given cross sectional area) is blowing air out of the room. If air displacement rate of the fan is given(CFM or m3/hr), is it possible to calculate the pressure differential that it can create between inside the room and outside the room ?

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If air displacement rate of the fan is given(CFM or m3/hr), is it possible to calculate the pressure differential that it can create between inside the room and outside the room ?

If you assume a constant volumetric air displacement rate (CFM or m3/hr), the calculation would yield zero air in the room after a certain amount of time (volume/flow rate). Of course this is not realistic, in a real situation the pressure in the room would approach a non-zero minimum value that would depend upon fan speed, impeller design and the design of the structure surrounding the impeller.

The following link shows a graph of how pressure differential relates to displacement rate for a set of real fans: http://botanical.com/hydro/air/graphics/canfan-cfm-static.gif

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  • $\begingroup$ Regarding "design of the structure surrounding the impeller" how does width of wall affect ? Zero thick wall to N inches thick wall (so that fan is like placed in the middle of a wind tunnel) Is there any relevant publication I can read about ? $\endgroup$ – Jean Apr 28 '14 at 17:13

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