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TRG-TRC001-EN 47
period six
Psychrometric Analyses
notes
This supply air mixes with room air along the part-load 0.70 SHR line from E to
A, arriving at the desired room conditions A. Now, if the room’s latent heat gain
were also changed, the resulting room conditions would not fall exactly on A,
but on the appropriate SHR line that runs through E.
Adding reheat permits better room humidity control at various part-load
conditions while maintaining room dry-bulb temperature control. Realize,
however, that this system uses more energy than the previous constant-volume
system with a modulating cooling coil: it constantly cools the supply air to
56.5°F, then reheats the air as necessary when the building sensible load drops.
Another method of improving the constant-volume system's ability to control
room humidity is to bypass mixed air around the cooling coil. In this example,
face-and-bypass dampers are placed in front of the cooling coil and used to
vary the portion of the supply air that actually passes through the coil, thus
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Figure 75
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Figure 76