HUMIDIFICATION
GRreqd = (WGR/ SpV) Room air – (WGR / SpV) Supply Air
Lbreqd = (Wlb / SpV) Room air – (Wlb / SpV) Supply Air
Qsteam = (Qair x GRreqd x 60) / 7000
Qsteam = Qair x Lbreqd x 60
Where
• GRreqd = Grains of Moisture Required (Gr H2O per Cu-ft of air)
• Lbreqd = Pounds of Moisture Required (Lb H2O per Cu-ft of air)
• Qair = Air Flow Rate (CFM)
• Qsteam = Steam Flow Rate (Lb per hour)
• SpV = Specific Volume of Air (Cu-ft per lb of dry air)
• ▲Wlb = Specific Humidity (lb-H2O per lb of dry air)
• ▲WGr = Specific Humidity (Gr. H2O per lb of dry air)
Humidifier Sensible Heat Gain
GRreqd = (WGR/ SpV) Room air – (WGR / SpV) Supply Air
Lbreqd = (Wlb / SpV) Room air – (Wlb / SpV) Supply Air
Qsteam = (Qair x GRreqd x 60) / 7000
Qsteam = Qair x Lbreqd x 60
Where
• GRreqd = Grains of Moisture Required (Gr H2O per Cu-ft of air)
• Lbreqd = Pounds of Moisture Required (Lb H2O per Cu-ft of air)
• Qair = Air Flow Rate (CFM)
• Qsteam = Steam Flow Rate (Lb per hour)
• SpV = Specific Volume of Air (Cu-ft per lb of dry air)
• ▲Wlb = Specific Humidity (lb-H2O per lb of dry air)
• ▲WGr = Specific Humidity (Gr. H2O per lb of dry air)
Humidifier Sensible Heat Gain
H = (0.244 x Q x ▲T) + (L x 380)
Where
• H = Sensible Heat Gain (Btu/Hr)
• Q = Steam Flow (Lb-Steam/Hr)
• ▲T = Steam Temperature - Supply Air Temperature (°F)
• L = Length of Humidifier Manifold (ft)
DEHUMIDIFIER EQUATIONS
A measure of the capacity of a dehumidifier is expressed in lbs per hour of moisture removal and is estimated by equation:
MRC = [Qair x (60 min/hr / Vs] x (GPPin - GPPout )) / 7000 grains/lb
Where,
• MRC = Moisture removal capacity (in Lb /hr)
• Qair = Volumetric rate of air (CFM)
• Vs = Specific volume of air (Cu-ft / lb)
• GPPin = Grains of moisture per pound of dry air in the inlet air stream
• GPPout = Grains of moisture per pound of dry air in the outlet air stream
The difference in (GPPin – GPPout) represents the grain "depression" or removal across the
dehumidifier.
Where
• H = Sensible Heat Gain (Btu/Hr)
• Q = Steam Flow (Lb-Steam/Hr)
• ▲T = Steam Temperature - Supply Air Temperature (°F)
• L = Length of Humidifier Manifold (ft)
DEHUMIDIFIER EQUATIONS
A measure of the capacity of a dehumidifier is expressed in lbs per hour of moisture removal and is estimated by equation:
MRC = [Qair x (60 min/hr / Vs] x (GPPin - GPPout )) / 7000 grains/lb
Where,
• MRC = Moisture removal capacity (in Lb /hr)
• Qair = Volumetric rate of air (CFM)
• Vs = Specific volume of air (Cu-ft / lb)
• GPPin = Grains of moisture per pound of dry air in the inlet air stream
• GPPout = Grains of moisture per pound of dry air in the outlet air stream
The difference in (GPPin – GPPout) represents the grain "depression" or removal across the
dehumidifier.
