Humid Air Properties  Psychrometrics
MATLAB Functions Library
Highprecision calculations of thermodynamic and psychrometric properties of humid air based on the latest mathematical models used in the ASHRAE formulation.
MAIN FEATURES

Performs all the calculations implementing the latest mathematical models used to generate the tables for humid air properties and thermodynamic properties of water in the 2009 ASHRAE Handbook of Fundamentals, namely:
 Thermodynamic and psychrometric property algorithms from the ASHRAE Research Project 1485.
 Properties of steam, water and ice from the Industrial Formulation IAPWSIF97, the Scientific Formulation IAPWS95, IAPWS Formulation 2008 and IAPWS Formulation 2006. Properties of dry air are from the NIST Reference equation of Lemmon et al.

Allows for 17 different combinations of thermodynamic properties to be entered as input parameters:
 Drybulb Temperature / Wetbulb Temperature
 Drybulb Temperature / Dew Point Temperature
 Drybulb Temperature / Relative Humidity
 Drybulb Temperature / Humidity Ratio
 Drybulb Temperature / Specific Enthalpy
 Drybulb Temperature / Specific Volume
 Wetbulb Temperature / Dew Point Temperature
 Wetbulb Temperature / Relative Humidity
 Wetbulb Temperature / Humidity Ratio
 Dew Point Temperature / Relative Humidity
 Dew Point Temperature / Specific Enthalpy
 Dew Point Temperature / Specific Volume
 Relative Humidity / Humidity Ratio
 Relative Humidity / Specific Enthalpy
 Relative Humidity / Specific Volume
 Humidity Ratio / Specific Enthalpy
 Humidity Ratio / Specific Volume
 Supports input parameters and calculation results in both the SI (metric) and IP (English) system of units.
 For each combination of input thermodynamic properties, validates the range of input variables.
RANGE OF VALIDITY
The valid range of calculations for thermodynamic and psychrometric properties is defined by the IAPWS (International Association for the Properties of Water and Steam) as shown on Figure 1.
Figure 1. Valid range for Humid Air Properties  Psychrometrics.
SYSTEM OF UNITS
Psychrometric variables in the SI (metric) system of units can be entered and/or the calculation results can be displayed in the following units (w = water, da = dry air):
 Pressure: Pa
 Temperature: K
 Humidity Ratio: kg(w)/kg)(da)
 Relative Humidity: decimal ratio
 Absolute Humidity: kg(w)/m³
 Parts per million: ppm
 Specific Volume: m³/kg
 Density: kg/m³
 Specific Enthalpy: J/kg
 Specific Entropy: J/(kg·K)
 Specific Isobaric Heat Capacity: J/(kg·K)
Psychrometric variables in the IP (English) system of units can be entered and/or the calculation results can be displayed in the following units (w = water, da = dry air):
 Pressure: psi
 Temperature: °F
 Humidity Ratio: lb(w)/lb(da)
 Relative Humidity: decimal ratio
 Absolute Humidity: lb(w)/ft³
 Parts per million: ppm
 Specific Volume: ft³/lb
 Density: lb/ft³
 Specific Enthalpy: Btu/lb
 Specific Entropy: Btu/(lb·°R)
 Specific Isobaric Heat Capacity: Btu/(lb·°R)
Output Variables
 DryBulb Temperature
 WetBulb Temperature
 Dew/Frost Point Temperature
 Partial Pressure of Water Vapor in Humid Air
 Partial Pressure of Dry Air in Humid Air
 Partial Saturation Water Vapor Pressure
 Mole Fraction of Dry Air in Humid Air
 Mole Fraction of Water Vapor in Humid Air
 Mass Fraction of Dry Air in Humid Air
 Mass Fraction of Wate Vapor in Humid Air
 Humidity Ratio
 Saturation Humidity Ratio
 Relative Humidity
 Absolute Humidity
 Parts per million by weight
 Parts per million by volume
 Enhancement Factor
 Specific Volume of Humid Air
 Specific Volume of Dry Air
 Density of Humid Air
 Density of Dry Air
 Specific Enthalpy of Humid Air
 Specific Enthalpy of Dry Air
 Specific Entropy of Humid Air
 Specific Entropy of Dry Air
 Specific Internal Energy of Humid Air
 Specific Internal Energy of Dry Air
 Specific Isobaric Heat Capacity of Humid Air
 Compressibility of Humid Air
 Specific Enthalpy of Liquid Water
 Specific Enthalpy of Saturated Liquid Water
 Specific Enthalpy of Saturated Water Vapor (for T ≥ 273.15 K / 32 °F)
 Specific Entropy of Liquid Water
 Specific Entropy of Saturated Liquid Water
 Specific Entropy of Saturated Water Vapor (for T ≥ 273.15 K / 32 °F)
 Specific Volume of Liquid Water
 Specific Volume of Saturated Liquid Water
 Specific Volume of Saturated Water Vapor (for T ≥ 273.15 K / 32 °F)
 Saturation Pressure of Water
 Saturation Temperature of Water
 Specific Enthalpy of Saturated Ice
 Specific Enthalpy of Saturated Water Vapor (for T ≤ 273.15 K / 32 °F )
 Specific Entropy of Saturated Ice
 Specific Entropy of Saturated Water Vapor (for T ≤ 273.15 K / 32 °F )
 Specific Volume of Saturated Ice
 Specific Volume of Saturated Water Vapor (for T ≤ 273.15 K / 32 °F )
 Melting Pressure of Ice
 Sublimation Pressure of Ice
 Melting Temperature of Ice
 Sublimation Temperature of Ice
Range of Input/Output Variables (SI)
Property

Valid range

Units

Pressure

10 ≤ P ≤ 10.0E6

Pa

Drybulb Temperature

130 ≤ Tdb ≤ 623.15

K

Wetbulb Temperature

130 ≤ Tdb ≤ 623.15

K

Dew Point Temperature

130 ≤ Td ≤ 623.15

K

Relative Humidity

0 ≤ PHI ≤ 1

(decimal ratio)

Humidity Ratio

0 ≤ W ≤ 10

kg/kg

Specific Enthalpy

311357 ≤ h ≤ 32135848

J/kg

Specific Volume

1.469E3 ≤ v ≤ 3.055E5

m³/kg

Range of Input/Output Variables (IP)
Property

Valid range

Units

Pressure

0.00145 ≤ P ≤ 1450.4

psi

Drybulb Temperature

225.67 ≤ Tdb ≤ 662.0

°F

Wetbulb Temperature

225.67 ≤ Twb ≤ 662.0

°F

Dew Point Temperature

225.67 ≤ Td ≤ 662.0

°F

Relative Humidity

0 ≤ PHI ≤ 1

(decimal ratio)

Humidity Ratio

0 ≤ W ≤ 10

lb/lb

Specific Enthalpy

126.174 ≤ h ≤ 13823.61

Btu/lb

Specific Volume

2.353E2 ≤ v ≤ 4.893E6

ft³/lb

References
 American Society of Heating; Owen, Mark. S.: 2009 ASHRAE Handbook: Fundamentals. ASHRAE (2009)
 Herrmann , Sebastian .; Kretzschmar, HansJoachim.; Gatley, Donald P.: Thermodynamic properties of real moist air, dry air, steam, water, and ice (RP1485). HVAC and R Research, (2011).
 Herrmann, S.; Kretzschmar, H.J.; Teske, V.; Vogel, E.; Ulbig, P.; Span, R.; Gatley, D.P.: Determination of Thermodynamic and Transport Properties for Humid Air for PowerCycle Calculations. PTBVerlag, Braunschweig (2009).
 Lemmon, E. W.; Jacobsen, R. T.; Penoncello, S. G.; Friend, D. G.: Thermodynamic Properties of Air and Mixture of Nitrogen, Argon, and Oxygen from 60 to 2000 K at Pressures to 2000 MPa. J. Phys. Chem. Ref. Data 29, 331385 (2000).
 Nelson, H.F.; Sauer, H.J.: Formulation of HighTemperature Properties for Moist Air. HVAC and R Research 8, 311334 (2002).
 Wagner, W.; Pruß, A.: The IAPWS Formulation 1995 for the Thermodynamic Properties of Ordinary Water Substance for General and Scientific Use. J. Phys. Chem. Ref. Data 31, 387535 (2002).
 Wagner, W.; Kretzschmar, H.J.: International Steam Tables. Springer, Berlin (2008).

Example of function application in Matlab
Input combination: Pressure, DryBulb Temperature, Humidity Ratio

Example of function application in Matlab
Input combination: Pressure, Dew Point Temperature, Specific Enthalpy

Example of function application in Matlab
Input combination: Pressure, Humidity Ratio, Specific Volume

Example of function application in Matlab
Functions dependent on Temperature Range

Example of Plot Data
Humidity Ratio as a function of Pressure, Temperature, Relative Humidity

Example of Plot Data
Enhancement factor as a function of Pressure, Temperature and Humidity Ratio

Example of Plot Data
Enthalpy as a function of Pressure, Temperature and Humidity Ratio
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Humid Air Properties  Psychrometrics MATLAB Functions Library.
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