steamtab
SteamTab Duo Functions
The SteamTab Duo 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 Duos
easy-to-use dialog boxes to automatically generate the appropriate function call with the
correct arguments.
SteamTab Duo functions are divided into three categories:
- 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.
- 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.
- 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.
Note
All SteamTab Duo functions based on the scientific formulation (IAPWS-95)
begin with the prefix ST, and all of the SteamTab Duo functions based on
the industrial formulation (IAPWS-IF97) begin with the prefix AST.
The following table gives a quick overview of these functions and their calling
sequence.
Table
1: SteamTab Duo Functions
| Scientific |
Industrial |
Calculates Property |
| Saturated vapor, liquid and two-phase
functions |
| STTSAT |
ASTTSAT |
at specified temperature and quality |
| STPSAT |
ASTPSAT |
at specified pressure and quality |
| Superheated or subcooled functions |
| STTP |
ASTTP |
at specified temperature and pressure (T-P) |
| STTV |
ASTTV |
at specified temperature and specific volume (T-V) |
| STTV |
ASTTV |
at specified temperature and enthalpy (T-H) |
| STTS |
ASTTS |
at specified temperature and entropy (T-S) |
| STTU |
ASTTU |
at specified temperature and internal energy (T-U) |
| STPV |
ASTPV |
at specified pressure and specific volume (P-V) |
| STPH |
ASTPH |
at specified pressure and enthalpy (P-H) |
| STPS |
ASTPS |
at specified pressure and entropy (P-S) |
| STPU |
ASTPU |
at specified pressure and internal energy (P-U) |
| Constant property functions |
| STMW |
ASTMW |
molecular weight |
| STTC |
ASTTC |
critical temperature |
| STPC |
ASTPC |
critical pressure |
| STVC |
ASTVC |
critical specific volume |
| STRC |
ASTRC |
critical specific density |
| STZC |
ASTZC |
critical compressibility factor |
| STTPT |
ASTTPT |
triple point temperature |
| STTPP |
ASTTPP |
triple point pressure |
The SteamTab Duo 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
| Property |
Metric/SI Units |
English Units |
| Temperature |
°C |
°F |
| Pressure |
bar |
psia |
| Volume |
m3/kg |
ft3/lb |
| Density |
kg/m3 |
lb/ft3 |
| Compressibility factor |
dimensionless |
dimensionless |
| Helmoltz free energy |
kJ/kg |
Btu/lb |
| Entropy |
kJ/(kg.°C) |
Btu/(lb.°F) |
| Internal Energy |
kJ/kg |
Btu/lb |
| Enthalpy |
kJ/kg |
Btu/lb |
| Gibbs free energy |
kJ/kg |
Btu/lb |
| Heat capacity at constant volume |
kJ/(kg.°C) |
Btu/(lb.°F) |
| Heat Capacity at constant pressure |
kJ/(kg.°C) |
Btu/(lb.°F) |
| Speed of sound |
m/s |
ft/s |
| Coefficient of thermal expansion |
1/°C |
1/°F |
| Isothermal compressibility |
1/bar |
1/psia |
| Partial derivative of pressure with temperature |
bar/°C |
psia/°F |
| Partial derivative of volume with temperature |
m3/(kg.°C) |
ft3/(lb.°F) |
| Partial derivative of volume with pressure |
m3/(kg.bar) |
ft3/(lb.°F) |
| Viscosity (dynamic) |
micro-Pa.s |
lb/(ft.hr) |
| Thermal conductivity |
W/(m.°C) |
Btu/(hr.ft.°F) |
| Surface Tension |
N/m |
N/m |
| Prandtl number |
dimensionless |
dimensionless |
| Static dielectric constant |
dimensionless |
dimensionless |
| Isothermal Joule-Thomson coefficient |
kJ/(kg.bar) |
Btu/(lb.psia) |
| Joule-Thomson coefficient |
°C/bar |
°F/psia |
| Quality (vapor-fraction) |
fraction |
fraction |