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SteamTab Functions

The SteamTab add-in package is based on a set of 19 core functions that together calculate over 30 thermodynamic and transport properties of steam. You can use these functions directly in your spreadsheet or you can use SteamTab’s easy-to-use dialog boxes to automatically generate the appropriate function call with the correct arguments.

SteamTab functions are divided into three categories:

  1. Functions for saturated vapor, liquid or two-phase properties (2 functions)
    These two functions calculate vapor, liquid and two-phase properties from the triple point up to the critical point. You can choose either temperature or pressure as the independent variable.
  2. Functions for superheated vapor or subcooled liquid properties (9 functions)
    The functions in this category provide you with a rich set of tools for conducting several constant-property processes. Depending on the choice of independent variables, you can model isentropic, isenthalpic, constant volume, or constant internal energy processes.
  3. Functions for constant steam properties (8 functions)
    The 8 functions in this category give you access to fundamental steam properties that are not functions of temperature or pressure, such as, molecular weight, critical properties, and triple point properties.

The following table gives a quick overview of these functions and their calling sequence.

Table 1: SteamTab Functions
FunctionCalculates Property
Saturated vapor, liquid and two-phase functions
STTSATat specified temperature and quality
STPSATat specified pressure and quality
Superheated or subcooled functions
STTPat specified temperature and pressure (T-P)
STTVat specified temperature and specific volume (T-V)
STTHat specified temperature and enthalpy (T-H)
STTSat specified temperature and entropy (T-S)
STTUat specified temperature and internal energy (T-U)
STPVat specified pressure and specific volume (P-V)
STPHat specified pressure and enthalpy (P-H)
STPSat specified pressure and entropy (P-S)
STPUat specified pressure and internal energy (P-U)
Constant property functions
STMWmolecular weight
STTCcritical temperature
STPCcritical pressure
STVCcritical specific volume
STRCcritical specific density
STZCcritical compressibility factor
STTPTtriple point temperature
STTPPtriple point pressure

The SteamTab functions return the requested property in either Metric/SI or English units. The thermodynamic and transport properties of steam and the units in which they are available is shown in the following table.

Table 2: Thermodynamic and Transport Properties of Water and Steam
PropertyMetric/SI Units English Units
Compressibility factordimensionlessdimensionless
Helmoltz free energykJ/kgBtu/lb
Internal EnergykJ/kgBtu/lb
Gibbs free energykJ/kgBtu/lb
Heat capacity at constant volumekJ/(kg.°C)Btu/(lb.°F)
Heat Capacity at constant pressurekJ/(kg.°C)Btu/(lb.°F)
Speed of soundm/sft/s
Coefficient of thermal expansion1/°C1/°F
Isothermal compressibility1/bar1/psia
Partial derivative of pressure with temperaturebar/°Cpsia/°F
Partial derivative of volume with temperaturem3/(kg.°C)ft3/(lb.°F)
Partial derivative of volume with pressurem3/( ft3/(lb.°F)
Viscosity (dynamic)micro-Pa.slb/(
Thermal conductivityW/(m.°C)Btu/(hr.ft.°F)
Surface TensionN/mN/m
Prandtl numberdimensionlessdimensionless
Static dielectric constantdimensionlessdimensionless
Isothermal Joule-Thomson coefficientkJ/(
Joule-Thomson coefficient°C/bar°F/psia
Quality (vapor-fraction)fractionfraction
Isentropic exponentdimensionlessdimensionless
Latent heat of vaporizationkJ/kgBtu/lb