DOE-2 Engineers Manual Version 2.1A - DOE-2.com

This is the supply air humidity ratio required to maintain the specified
return air humidity ratio. Thus, the resultant mixed air humidity ratio
is
WM = (PO * HUMRAT) + [(1.0 - PO) * WRMIN], (IV.I55)
and the humidification heating energy is
QHUM = (WM - WMM) * CONS(2) * CFM. (IV.I56)
The total heating energy is calculated as the sum of the sensible and
latent components
where
QH = {CFM * 0 * [H(TM, WM) - H(TC,WM)]} + QHUM, (IV.I5?)
o 50.0
= V (TM ,WM, PATM)
the density of air at TM, WM, and PATM times 60
minutes/hour, and
H = the enthalphy of air at the conditions indicated.
G. If the system is in the cooling mode, calculate the coil surface temperature
and its humidity ratio at saturation, the mixed air humidity ratio,
the sensible cooling energy, and the dehumidification energy, if present.
If the coil entering air temperature (TM) is larger than the coil exit
air temperature (TC), the air handler is in the net cooling mode. It is
necessary to determine if the coil is dry or wet and whether or not humidity
control will require further depression of the cooling coil exit air
temperature. The contact between the cooling coil and the mixed air is
characterized by the coil bypass factor (CBF). This value is assumed to
be the product of the design bypass factor (COIL-BF) and two modifier
functions to correct for off-design (off-rated) conditions
where
CBF = COIL-BF * CVAL(COIL-BF-FT,EWB,EDB)
* CVAL(COIL-BF-FCFM,PLRCFM),
(IV.I58)
COIL-BF-FT is a correct ion funct ion to the coil bypass factor to
adjust for off-rated entering wet-bulb and dry-bulb temperatures,
IV.55