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 ?
1 Answer
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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 ? $\endgroup$– JeanApr 28, 2014 at 17:13