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Hydraulics, Pipe Flow, Industrial HVAC & Utility Systems: Mister Mech Mentor, Vol. 1
James A. Wingate
James A. Wingate
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ASME Press
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Our goal here is to be able to make a suitably accurate estimate of the amounts of airflow entering and leaving a particular room in order to design a heating, ventilating, and air conditioning (HVAC) system that can maintain the air pressure in that room at a predetermined constant value with respect to the pressure(s) of its surrounding boundary air volumes. We will not concern ourselves with the heating, cooling, or humidity control of any of those air volumes in this section; just the room's relative air pressure.

The candidate air streams into and out of a room are: supply air, return air, exhaust air, makeup air, infiltration into a negative pressure airspace and exfiltration from a positive pressure airspace. Not all streams exist in every case.

The example problem solved later in this chapter is illustrated and defined in the calculation. Although the example selected was rather simple, the same procedure applies to any enclosed volume of air, and to positive differentials as well as negative ones. Just formulate the algebraic sum of all airstreams in and out, as a function of the stream's pressure drop due to flow, solving finally for the unknown stream flowrate.

Statement of Problem
Conclusion Required Exhaust Fan Flowrate @ the Design Conditions
Final Thoughts
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