Coil Bypass Factor and Apparatus Dew Point

Bypass factor BF = (t_lvg - t_adp)/(t_ent - t_adp), contact factor CF = 1 - BF, off the apparatus dew point (coil-surface temperature). 80 -> 55 F off a 50 F ADP -> BF 0.167, CF 0.833; a shallower coil bypasses more and dehumidifies worse. A design aid; the coil rating governs.

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Formula and source

BF = (t_lvg - t_adp) / (t_ent - t_adp); CF = 1 - BF.

The coil bypass / contact factor and apparatus-dew-point definition from the ASHRAE Handbook - Fundamentals, by name.

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