Humid Air¶
The CoolProp project not only supports Pure Fluids wrapped by the EngCoolProp EC_Fluid object EC_Fluid Functions, but also Humid Air wrapped by the EngCoolProp EC_Humid_Air object EC_Humid_Air Functions.
The most simple way to create an EC_Humid_Air object is:
from engcoolprop.ec_humid_air import EC_Humid_Air
HA = EC_Humid_Air()
However, the object can be initialized in a number of ways that all result in the required three inputs to the CoolProp HAPropsSI interface. (see resulting inputs as comment after EC_Humid_Air initialization call):
*) Can initialize with no input parameters
EC_Humid_Air() # T=536.4, P=14.6959, RelHum=0.5
*) Can omit pressure (P) and 1 atm will be assumed
EC_Humid_Air(T=600, R=1) # T=600, R=1, P=14.6959
*) Can append "degF" to any temperature and degR will result
EC_Humid_Air(TdegF=70, RelHum=.6) # T=529.67, RelHum=0.6, P=14.6959
*) Can use all synonyms for inputs (e.g. T_db, Tdb, T)
EC_Humid_Air(P=14.7, RH=.3, Tdb=530) # P=14.7, RH=0.3, Tdb=530
Input Parameters¶
To see the legal input parameters for EC_Humid_Air, run the following script:
from engcoolprop.ec_humid_air import EC_Humid_Air
ha = EC_Humid_Air()
ha.print_input_params()
with results:
+----------------------------------------------------------------------------+
| ---------------------- Humid Air Input Parameters ---------------------- |
+----------------------------------------------------------------------------+
Tdb degR Dry-Bulb Temperature ::AKA {'T_db', 'T'}
WetBulb degR Wet-Bulb Temperature ::AKA {'B', 'Twb', 'T_wb'}
DewPoint degR Dew-Point Temperature ::AKA {'T_dp', 'Tdp', 'D'}
P psia Pressure
P_w psia Partial pressure of water vapor
Vda ft^3/lbm dry air Mixture volume per unit dry air ::AKA {'V'}
Vha ft^3/lbm humid air Mixture volume per unit humid air
Hda BTU/lbm dry air Mixture enthalpy per dry air ::AKA {'H', 'Enthalpy'}
Hha BTU/lbm humid air Mixture enthalpy per humid air
Sda BTU/lbm dry air/degR Mixture entropy per unit dry air ::AKA {'Entropy', 'S'}
Sha BTU/lbm humid air/degR Mixture entropy per unit humid air
RelHum Relative humidity in range [0, 1] ::AKA {'RH', 'R'}
HumRat lbm water/lbm dry air Humidity Ratio ::AKA {'W', 'Omega'}
Y mol water/mol humid air Water mole fraction ::AKA {'psi_w'}
Note that Pressure(P) must ALWAYS be input and that for the remaining 2 inputs, not all input pairs are compatible. Dry bulb temperature(Tdb) will work with ALL other input parameters, however, the rest of the input parameters are more limited. The following shows what pairs are known to work and fail in order of least to most limited:
Tdb WORKS: DewPoint, Hda, Hha, HumRat, P_w, RelHum, Sda, Sha, Vda, Vha, WetBulb, Y
FAILS:
RelHum WORKS: Hda, Hha, P_w, Sda, Sha, Tdb, Vda, Vha, WetBulb, Y
FAILS: DewPoint, HumRat
DewPoint WORKS: Hda, Hha, Sda, Sha, Tdb, Vda, Vha, WetBulb
FAILS: HumRat, P_w, RelHum, Y
HumRat WORKS: Hda, Hha, Sda, Sha, Tdb, Vda, Vha, WetBulb
FAILS: DewPoint, P_w, RelHum, Y
Hda WORKS: DewPoint, HumRat, RelHum, Tdb
FAILS: Hha, P_w, Sda, Sha, Vda, Vha, WetBulb, Y
Hha WORKS: DewPoint, HumRat, RelHum, Tdb
FAILS: Hda, P_w, Sda, Sha, Vda, Vha, WetBulb, Y
Sda WORKS: DewPoint, HumRat, RelHum, Tdb
FAILS: Hda, Hha, P_w, Sha, Vda, Vha, WetBulb, Y
Sha WORKS: DewPoint, HumRat, RelHum, Tdb
FAILS: Hda, Hha, P_w, Sda, Vda, Vha, WetBulb, Y
Vda WORKS: DewPoint, HumRat, RelHum, Tdb
FAILS: Hda, Hha, P_w, Sda, Sha, Vha, WetBulb, Y
Vha WORKS: DewPoint, HumRat, RelHum, Tdb
FAILS: Hda, Hha, P_w, Sda, Sha, Vda, WetBulb, Y
WetBulb WORKS: DewPoint, HumRat, RelHum, Tdb
FAILS: Hda, Hha, P_w, Sda, Sha, Vda, Vha, Y
P_w WORKS: RelHum, Tdb
FAILS: DewPoint, Hda, Hha, HumRat, Sda, Sha, Vda, Vha, WetBulb, Y
Y WORKS: RelHum, Tdb
FAILS: DewPoint, Hda, Hha, HumRat, P_w, Sda, Sha, Vda, Vha, WetBulb
Output Parameters¶
To see all output parameters, run the following script:
from engcoolprop.ec_humid_air import EC_Humid_Air
ha = EC_Humid_Air()
ha.print_output_params()
with results:
+-----------------------------------------------------------------------------+
| ---------------------- Humid Air Output Parameters ---------------------- |
+-----------------------------------------------------------------------------+
Tdb degR Dry-Bulb Temperature ::AKA {'T_db', 'T'}
WetBulb degR Wet-Bulb Temperature ::AKA {'B', 'Twb', 'T_wb'}
DewPoint degR Dew-Point Temperature ::AKA {'T_dp', 'Tdp', 'D'}
P psia Pressure
P_w psia Partial pressure of water vapor
Vda ft^3/lbm dry air Mixture volume per unit dry air ::AKA {'V'}
Vha ft^3/lbm humid air Mixture volume per unit humid air
cp BTU/lbm dry air/degR Mixture Cp per unit dry air ::AKA {'C'}
cp_ha BTU/lbm humid air/degR Mixture Cp per unit humid air ::AKA {'Cha'}
CV BTU/lbm dry air/degR Mixture Cv per unit dry air
CVha BTU/lbm humid air/degR Mixture Cv per unit humid air ::AKA {'cv_ha'}
Hda BTU/lbm dry air Mixture enthalpy per dry air ::AKA {'H', 'Enthalpy'}
Hha BTU/lbm humid air Mixture enthalpy per humid air
Sda BTU/lbm dry air/degR Mixture entropy per unit dry air ::AKA {'Entropy', 'S'}
Sha BTU/lbm humid air/degR Mixture entropy per unit humid air
Cond BTU/ft-hr-R Mixture thermal conductivity ::AKA {'Conductivity', 'K', 'k'}
Visc [1.0E5 * lbm/ft-sec] Mixture viscosity ::AKA {'mu', 'M'}
RelHum Relative humidity in range [0, 1] ::AKA {'RH', 'R'}
HumRat lbm water/lbm dry air Humidity Ratio ::AKA {'W', 'Omega'}
Y mol water/mol humid air Water mole fraction ::AKA {'psi_w'}
Z Compressibility factor (Z=pv/(RT))
State Point¶
Creating a listing of properties at a given state point is done by calling printProps():
from engcoolprop.ec_humid_air import EC_Humid_Air
ha = EC_Humid_Air()
ha.printProps()
Resulting In:
+------------------------------------------------------------------------+
| ---- State Point for Humid Air (T=536.4, P=14.6959, RelHum=0.5) ---- |
+------------------------------------------------------------------------+
Tdb = 536.4 degR :: Dry-Bulb Temperature (76.7 degF)
WetBulb = 523.638 degR :: Wet-Bulb Temperature (64.0 degF)
DewPoint = 516.383 degR :: Dew-Point Temperature (56.7 degF)
P = 14.6959 psia :: Pressure (1 atm)
P_w = 0.228794 psia :: Partial pressure of water vapor (0.0155686 atm)
Vda = 13.7316 ft^3/lbm dry air :: Mixture volume per unit dry air
Vha = 13.5978 ft^3/lbm humid air :: Mixture volume per unit humid air
cp = 0.244776 BTU/lbm dry air/degR :: Mixture Cp per unit dry air
cp_ha = 0.242391 BTU/lbm humid air/degR :: Mixture Cp per unit humid air
CV = 0.174785 BTU/lbm dry air/degR :: Mixture Cv per unit dry air
CVha = 0.173083 BTU/lbm humid air/degR :: Mixture Cv per unit humid air
Hda = 21.5138 BTU/lbm dry air :: Mixture enthalpy per dry air
Hha = 21.3042 BTU/lbm humid air :: Mixture enthalpy per humid air
Sda = 0.0428596 BTU/lbm dry air/degR :: Mixture entropy per unit dry air
Sha = 0.0424422 BTU/lbm humid air/degR :: Mixture entropy per unit humid air
Cond = 0.0151596 BTU/ft-hr-R :: Mixture thermal conductivity
Visc = 1.23324 [1.0E5 * lbm/ft-sec] :: Mixture viscosity
RelHum = 0.5 :: Relative humidity in range [0, 1]
HumRat = 0.00983592 lbm water/lbm dry air :: Humidity Ratio
Y = 0.0155686 mol water/mol humid air :: Water mole fraction
Z = 0.999629 :: Compressibility factor (Z=pv/(RT))
printSIUnits¶
Although EngCoolProp was created to promote English units when using CoolProp , it is often helpful to see properties in SI units.
For that reason, all the EngCoolProp models have a method called printSIUnits that will output the State Point with SI units. The script below shows the result of calling printSIUnits:
from engcoolprop.ec_humid_air import EC_Humid_Air
ha = EC_Humid_Air()
ha.printSIProps()
Output:
+---------------------------------------------------------------------+
| ---- State Point for Humid Air (T=298, P=101325, RelHum=0.5) ---- |
+---------------------------------------------------------------------+
Tdb = 298 K :: Dry-Bulb Temperature
WetBulb = 290.91 K :: Wet-Bulb Temperature
DewPoint = 286.879 K :: Dew-Point Temperature
P = 101325 Pa :: Pressure
P_w = 1577.48 Pa :: Partial pressure of water vapor
Vda = 0.857236 m^3 /kg dry air :: Mixture volume per unit dry air
Vha = 0.848887 m^3 /kg humid air :: Mixture volume per unit humid air
cp = 1024.83 J/kg dry air/K :: Mixture Cp per unit dry air
cp_ha = 1014.84 J/kg humid air/K :: Mixture Cp per unit humid air
CV = 731.789 J/kg dry air/K :: Mixture Cv per unit dry air
CVha = 724.661 J/kg humid air/K :: Mixture Cv per unit humid air
Hda = 50041.1 J/kg dry air :: Mixture enthalpy per dry air
Hha = 49553.7 J/kg humid air :: Mixture enthalpy per humid air
Sda = 179.445 J/kg dry air/K :: Mixture entropy per unit dry air
Sha = 177.697 J/kg humid air/K :: Mixture entropy per unit humid air
Cond = 0.0262197 W/m/K :: Mixture thermal conductivity
Visc = 1.83527e-05 Pa-s :: Mixture viscosity
RelHum = 0.5 :: Relative humidity in range [0, 1]
HumRat = 0.00983592 kg water/kg dry air :: Humidity Ratio
Y = 0.0155686 mol water/mol humid air :: Water mole fraction
Z = 0.999629 :: Compressibility factor (Z=pv/(RT))
Making Plots¶
An easy way to make plots is to use the matplotlib package.
To install matplotlib give the commands:
pip install matplotlib
... OR to upgrade...
pip install --upgrade matplotlib
The example below will plot the partial pressure of water vapor (P_w) over a range of states.:
import matplotlib.pyplot as plt
from engcoolprop.ec_humid_air import EC_Humid_Air
HA = EC_Humid_Air()
for RelHum in [1.0, 0.7, 0.5, 0.3, 0.1]:
tL = [500 + i for i in range(61)]
hL = []
for T in tL:
HA.setProps( Tdb=T, RelHum=RelHum)
hL.append( HA.P_w )
plt.plot( tL, hL, label='RelHum=%g'%RelHum)
plt.grid( True )
plt.title( 'Humid Air Water Partial Pressure')
plt.xlabel( 'Dry Bulb Temperature (degR)')
plt.ylabel( 'Water Partial Pressure (psia)')
plt.legend( loc='best' )
plt.savefig( 'water_partial_pressure.png', dpi=200)
plt.show()
