Humid Air Properties

Psychrometrics

MATLAB Functions Library

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Humid Air Properties

Psychrometrics

MATLAB Functions Library

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Requirements

  • •
    Windows Versions: Windows 11, Windows 10
  • •
    Matlab Versions: MATLAB 7.8 (R2009a) and subsequent versions.
  • •
    Library available in 32-bit and 64-bit versions.

Features

  • •
    Implements the latest mathematical models to simulate the physics of water, water vapor, humid air, dry air and ice.
  • •
    More than 400 Library Functions to be used inside the Matlab environment to generate high-precision calculations or plots.
  • •
    Calculates 50 psychrometric quantities of humid air, dry air, water, water vapor and ice.
  • •
    Allows for 17 combinations of thermodynamic properties to be entered.
  • •
    Each function validates against the range of values entered in case of an invalid input or result.
  • •
    Includes functions for the SI (metric) and I-P (English) System of Units.
  • •
    Numerical results obtained are suitable for engineering, scientific, industrial or academic use.

Humid Air Properties - Psychrometrics
MATLAB Functions Library



High-precision 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 IAPWS-IF97, the Scientific Formulation IAPWS-95, 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:

    • Dry-bulb Temperature / Wet-bulb Temperature

    • Dry-bulb Temperature / Dew Point Temperature

    • Dry-bulb Temperature / Relative Humidity

    • Dry-bulb Temperature / Humidity Ratio

    • Dry-bulb Temperature / Specific Enthalpy

    • Dry-bulb Temperature / Specific Volume

    • Wet-bulb Temperature / Dew Point Temperature

    • Wet-bulb Temperature / Relative Humidity

    • Wet-bulb 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 I-P (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 I-P (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

  • Dry-Bulb Temperature

  • Wet-Bulb 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

Dry-bulb Temperature

130 ≤ Tdb ≤ 623.15

K

Wet-bulb 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

1.469E-3 ≤ v ≤ 3.055E5

m³/kg

Range of Input/Output Variables (I-P)

Property

Valid range

Units

Pressure

0.00145 ≤ P ≤ 1450.4

psi

Dry-bulb Temperature

-225.67 ≤ Tdb ≤ 662.0

°F

Wet-bulb 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

2.353E-2 ≤ v ≤ 4.893E6

ft³/lb

References

  • American Society of Heating; Owen, Mark. S.: 2009 ASHRAE Handbook: Fundamentals. ASHRAE (2009)
  • Herrmann , Sebastian .; Kretzschmar, Hans-Joachim.; Gatley, Donald P.: Thermodynamic properties of real moist air, dry air, steam, water, and ice (RP-1485). 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 Power-Cycle Calculations. PTB-Verlag, 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, 331-385 (2000).
  • Nelson, H.F.; Sauer, H.J.: Formulation of High-Temperature Properties for Moist Air. HVAC and R Research 8, 311-334 (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, 387-535 (2002).
  • Wagner, W.; Kretzschmar, H.-J.: International Steam Tables. Springer, Berlin (2008).

Example of function application in Matlab

Input combinatoin: Pressure, Dry-Bulb Temperature, Humidity Ratio

Example of function application in Matlab

Example of function application in Matlab

Input combination: Pressure, Dew Point Temperature, Specific Enthalpy

Example of function application in Matlab

Example of function appli9cation in Matlab

Input ocmbination: Pressure, Humidity Ratio, Specific Volume

Example of function appli9cation in Matlab

Example of function application in Matlab

Functions dependent on Temperature Ramge

Example of function application in Matlab

Example of Plot Data

Humidity Ratio as function of Pressure, Temparature, Relative Humidity

Example of Plot Data

Example of Plot Data

Enhancement Factor as a function of Pressure, Temperature, and Humidity Ratio

Example of Plot Data

Example of Plot Data

Enthalpy as a function of Pressure, Temperature and Humidity Ratio

Example of Plot Data

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DOCUMENTS