Welcome to pyXSteam’s documentation!

Original Released by Magnus Holmgren for Matlab and Excel: <http://xsteam.sourceforge.net> and/or <http://www.x-eng.com>

XSteam provides (mostly) accurate steam and water properties from 0 - 1000 bar and from 0 - 2000 °C according to the [IAPWS release IF-97](http://www.iapws.org/relguide/IF97-Rev.pdf). For accuracy of the functions in different regions see IF-97 Page 4

Also includes thermal conductivity and viscosity, which are not part of the IF97 release. * Thermal Conductivity: (IAPWS 1998)

This Python Library is based on the original XSteam Library for Matlab and Excel from Magnus Holmgren, www.x-eng.com. We take no responsibilities for any errors in the code or damage thereby! See README.md for examples

Some effort has been made to include the refined function of more recent releases and also functions for calculations on heavy water. This includes: * IAPWS R4 * IAPWS R14

Notes

Density (rho)

Density is calculated as 1/v. See section 1.5 Volume

Viscosity

Viscosity is not part of IAPWS Steam IF97. Equations from “Revised Release on the IAPWS Formulation 1985 for the Viscosity of Ordinary Water Substance”, 2003 are used. Viscosity in the mixed region (4) is interpolated according to the density. This is not true since it will be two phases.

Thermal conductivity

Revised release on the IAPS Formulation 1985 for the Thermal Conductivity of ordinary water substance (IAPWS 1998)

Nomenclature

All Functions follow the same naming schema: First the wanted property, then a underscore _, then the wanted input properties Example: t_ph is temperature as a function of pressure and enthalpy. For a list of valid functions se bellow:

Property Description
t Temperature (°C or °F)
p Pressure (bar or psi)
h Enthalpy (kJ/kg or btu/lb)
v Specific volume (m3/kg or ft^3/lb)|
rho Density (kg/m3 or lb/ft^3)
s Specific entropy (kJ/(kg °C) or btu/(lb °F))
u Specific internal energy (kJ/kg or btu/lb)
Cp Specific isobaric heat capacity (kJ/(kg °C) or btu/(lb °F))
Cv Specific isochoric heat capacity (kJ/(kg °C) or btu/(lb °F))
w Speed of sound (m/s or ft/s)
my Viscosity (N s/m^2 or lbm/ft/hr)
tc Thermal Conductivity (W/(m °C) or btu/(h ft °F))
st Surface Tension (N/m or lb/ft)
x Vapor fraction
vx Vapor Volume Fraction

Available Functions

Temperature
Function Description
tsat_p Saturation temperature
t_ph Temperature as a function of pressure and enthalpy
t_ps Temperature as a function of pressure and entropy
t_hs Temperature as a function of enthalpy and entropy
Pressure
Function Description
psat_t Saturation pressure
p_hs Pressure as a function of h and s.
p_hrho Pressure as a function of h and rho. Very inaccurate for solid water region since it’s almost incompressible!
Enthalpy
Function Description
hV_p Saturated vapor enthalpy
hL_p Saturated liquid enthalpy
hV_t Saturated vapor enthalpy
hL_t Saturated liquid enthalpy
h_pt Enthalpy as a function of pressure and temperature
h_ps Enthalpy as a function of pressure and entropy
h_px Enthalpy as a function of pressure and vapor fraction
h_prho Enthalpy as a function of pressure and density. Observe for low temperatures (liquid) this equation has 2 solutions
h_tx Enthalpy as a function of temperature and vapor fraction
Specific volume
Function Description
vV_p Saturated vapor volume
vL_p Saturated liquid volume
vV_t Saturated vapor volume
vL_t Saturated liquid volume
v_pt Specific volume as a function of pressure and temperature
v_ph Specific volume as a function of pressure and enthalpy
v_ps Specific volume as a function of pressure and entropy
Density
Function Description
rhoV_p Saturated vapor density
rhoL_p Saturated liquid density
rhoV_t Saturated vapor density
rhoL_t Saturated liquid density
rho_pt Density as a function of pressure and temperature
rho_ph Density as a function of pressure and enthalpy
rho_ps Density as a function of pressure and entropy
Specific entropy
Function Description
sV_p Saturated vapor entropy
sL_p Saturated liquid entropy
sV_t Saturated vapor entropy
sL_t Saturated liquid entropy
s_pt Specific entropy as a function of pressure and temperature (Returns saturated vapor enthalpy if mixture)
s_ph Specific entropy as a function of pressure and enthalpy
Specific internal energy
Function Description
uV_p Saturated vapor internal energy
uL_p Saturated liquid internal energy
uV_t Saturated vapor internal energy
uL_t Saturated liquid internal energy
u_pt Specific internal energy as a function of pressure and temperature
u_ph Specific internal energy as a function of pressure and enthalpy
u_ps Specific internal energy as a function of pressure and entropy
Specific isobaric heat capacity
Function Description
CpV_p Saturated vapor heat capacity
CpL_p Saturated liquid heat capacity
CpV_t Saturated vapor heat capacity
CpL_t Saturated liquid heat capacity
Cp_pt Specific isobaric heat capacity as a function of pressure and temperature
Cp_ph Specific isobaric heat capacity as a function of pressure and enthalpy
Cp_ps Specific isobaric heat capacity as a function of pressure and entropy
Specific isochoric heat capacity
Function Description
CvV_p Saturated vapor isochoric heat capacity
CvL_p Saturated liquid isochoric heat capacity
CvV_t Saturated vapor isochoric heat capacity
CvL_t Saturated liquid isochoric heat capacity
Cv_pt Specific isochoric heat capacity as a function of pressure and temperature
Cv_ph Specific isochoric heat capacity as a function of pressure and enthalpy
Cv_ps Specific isochoric heat capacity as a function of pressure and entropy
Speed of sound
Function Description
wV_p Saturated vapor speed of sound
wL_p Saturated liquid speed of sound
wV_t Saturated vapor speed of sound
wL_t Saturated liquid speed of sound
w_pt Speed of sound as a function of pressure and temperature
w_ph Speed of sound as a function of pressure and enthalpy
w_ps Speed of sound as a function of pressure and entropy
Viscosity
Function Description
my_pt Viscosity as a function of pressure and temperature
my_ph Viscosity as a function of pressure and enthalpy
my_ps Viscosity as a function of pressure and entropy
Thermal Conductivity
Function Description
tcL_p Saturated vapor thermal conductivity
tcV_p Saturated liquid thermal conductivity
tcL_t Saturated vapor thermal conductivity
tcV_t Saturated liquid thermal conductivity
tc_pt Thermal conductivity as a function of pressure and temperature
tc_ph Thermal conductivity as a function of pressure and enthalpy
tc_hs Thermal conductivity as a function of enthalpy and entropy
Surface tension
Function Description
st_t Surface tension for two phase water/steam as a function of T
st_p Surface tension for two phase water/steam as a function of p
vapor fraction
Function Description
x_ph vapor fraction as a function of pressure and enthalpy
x_ps vapor fraction as a function of pressure and entropy
vapor volume fraction
Function Description
vx_ph vapor volume fraction as a function of pressure and enthalpy
vx_ps vapor volume fraction as a function of pressure and entropy
Pressure along the Melting and Sublimation Curves
Function Description
pmelt_t Pressure along the melting curve as a function of temperature
psubl_t Pressure along the sublimation curve as a function of temperature

Available Functions for Heavy Water

Function Description
my_rhoT Viscosity as a function of density and temperature
tc_rhoT Thermal conductivity as a function of density and temperature

pyXSteam package

Submodules
pyXSteam.XSteam module
pyXSteam.UnitConverter module
pyXSteam.Constants module
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__SPECIFIC_GAS_CONSTANT__ = 0.461526  # kJ kg^-1 K^-1
__CRITICAL_TEMPERATURE__ = 647.096  # K
__CRITICAL_PRESSURE__ = 22.06395  # MPa
__CRITICAL_DENSITY__ = 322  # kg m^-1
__TRIPLE_POINT_TEMPERATURE__ = 273.16  # K (Eq9 Page 7)
__TRIPLE_POINT_PRESSURE__ = 0.000611657  # MPa (Eq9 Page 7)
__TRIPLE_POINT_SPECIFIC_ENTHALPY__ = 0.611783E-3  # kJ kg^-1 (Eq10 Page 7)
# Released September 1992, Revision of the Release of 1992
__CRITICAL_TEMPERATURE_H20_1992__ = 647.096  # +-0.1 K
__CRITICAL_PRESSURE_H20_1992__ = 22.067  # + 0.27*(+-0.1)+-0.005 MPa
__CRITICAL_DENSITY_H20_1992__ = 322  # +-3 kg m^-1

__CRITICAL_TEMPERATURE_D20_1992__ = 643.847  # +-0.2 K
__CRITICAL_PRESSURE_D20_1992__ = 21.671  # + 0.27*(+-0.2)+-0.01 MPa
__CRITICAL_DENSITY_D20_1992__ = 356  # +-5 kg m^-1
# Other common constants used in calculations
__ABSOLUTE_ZERO_CELSIUS__ = -273.15  # °C
pyXSteam.Regions module
pyXSteam.RegionBorders module
pyXSteam.RegionSelection module
pyXSteam.TransportProperties module
pyXSteam.IAPWS_R4 module
pyXSteam.IAPWS_R14 module
Module contents

Tutorial and Demos

Usage

Simple Example:

from pyXSteam.XSteam import XSteam
steam_table = XSteam(XSteam.UNIT_SYSTEM_MKS)
print steam_table.hL_p(220.0)

By using the unitSystem Parameter, you can tell XSteam witch Unit System you are using.:

steam_table = XSteam(XSteam.UNIT_SYSTEM_MKS) # m/kg/sec/°C/bar/W
steam_table = XSteam(XSteam.UNIT_SYSTEM_FLS) # ft/lb/sec/°F/psi/btu
steam_table = XSteam(XSteam.UNIT_SYSTEM_BARE) # m/kg/sec/K/MPa/W

To enable logging, add the following lines to your code:

import logging
logger = logging.getLogger('pyXSteam')
logger.setLevel(logging.DEBUG) sh = logging.StreamHandler()
sh.setFormatter(logging.Formatter('%(name)s - %(levelname)s - %(message)s'))
logger.addHandler(sh)
Calculate single values

This is a simple example:

>>> from pyXSteam.XSteam import XSteam
>>> steam_table = XSteam(XSteam.UNIT_SYSTEM_MKS)
>>> steam_table.hL_p(220.0)
2021.909286172027
>>> steam_table.tcV_p(1)
0.02475366759235046
Generate Diagrams

Diagrams based on the calculated values can easily be created using numpy and matplotlib.

Example: To draw a T(p) diagram showing the saturation curve:

from pyXSteam.XSteam import XSteam
import matplotlib.pyplot as pyplot
import numpy as np
steam_table = XSteam(XSteam.UNIT_SYSTEM_MKS)
p = np.arange(-100.0, 250.0, 1.0)
ntsat_p = np.frompyfunc(steam_table.tsat_p, 1, 1)
tsat = ntsat_p(p)
line1, = pyplot.plot(tsat, p)
pyplot.xlabel("t")
pyplot.ylabel("p")
pyplot.setp(line1, linewidth=1, color='b')
pyplot.show()

For more demos, see pyXSteamDemo.py

Heavy Water functions

The functions to calculate values for heavy water are available through the class XSteamHW

>>> from pyXSteam.XSteamHW import XSteamHW
>>> steam_table = XSteamHW(XSteam.UNIT_SYSTEM_MKS)
>>> steam_table.my_rhoT(1.2, 300.0)

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""collection of demos presenting the functionality of pyXSteam"""
import time
import logging
from mpl_toolkits.mplot3d import Axes3D
import matplotlib.pyplot as pyplot
import numpy as np
from pyXSteam.XSteam import XSteam
from pyXSteam.XSteam_HW import XSteam_HW


def demo_simpel_values():
    """calculate values and print the results"""
    steam_table = XSteam(XSteam.UNIT_SYSTEM_MKS)
    # get saturated liquid enthalpy for a preasure of 220 bar
    print('hV_p(220.0) =', steam_table.hL_p(220.0))
    # get saturated vapour enthalpy for a preasure of 220 bar
    print('hV_p(220.0) =', steam_table.hV_p(220.0))
    print('tcL_p(1.0) =', steam_table.tcL_p(1.0))
    print('tcL_t(25.0) =', steam_table.tcL_t(25.0))
    print('tcV_p(1.0) =', steam_table.tcV_p(1.0))
    print('tcL_t(25.0) =', steam_table.tcV_t(25.0))
    print('tc_hs(100.0, 0.34) =', steam_table.tc_hs(100.0, 0.34))
    print('tc_ph(1.0, 100.0) =', steam_table.tc_ph(1.0, 100.0))
    print('tc_pt(1.0, 25.0) =', steam_table.tc_pt(1.0, 25.0))
    print('w_ps(1.0, 1.0) =', steam_table.w_ps(1.0, 1.0))


def demo_generate_ph_diagramm(path=None, precision=1.0):
    """Generate a p(h) Diagramm showing the Saturation Line"""
    steam_table = XSteam(XSteam.UNIT_SYSTEM_MKS)
    p_krit = steam_table.criticalPressure() - 0.0001  # minus 0.0001 or else hL_V returns NaN
    h_krit = steam_table.hL_p(p_krit)
    p = np.arange(0.0, 1000, precision)
    p2 = np.arange(0.5, p_krit, precision)
    vapor_fraction = np.arange(0.1, 1.0, 0.1)
    h = np.arange(200.0, 4500.0, 100.0)
    rho = np.arange(1, 15.0, precision * 2)
    nph_px = np.frompyfunc(steam_table.h_px, 2, 1)
    nph_pt = np.frompyfunc(steam_table.h_pt, 2, 1)
    nphL_p = np.frompyfunc(steam_table.hL_p, 1, 1)
    nphV_p = np.frompyfunc(steam_table.hV_p, 1, 1)
    npp_hrho = np.frompyfunc(steam_table.p_hrho, 2, 1)
    # Siede und Taulinie
    hL = nphL_p(p)
    hV = nphV_p(p)
    # Dampfgehalt
    for vf in vapor_fraction:
        h_px = nph_px(p2, vf)
        line, = pyplot.plot(h_px, p2)
        pyplot.setp(line, linewidth=1, color='g')
    # Temperatur
    for temp in range(0, 900, 30):
        h_pt = nph_pt(p, temp)
        line, = pyplot.plot(h_pt, p)
        pyplot.setp(line, linewidth=1, color='r')
    # Dichte
    for r in rho:
        p_hrho = npp_hrho(h, r)
        line, = pyplot.plot(h, p_hrho)
        pyplot.setp(line, linewidth=1, color='y')
    # Kritischer Punkt
    pyplot.plot([h_krit], [p_krit], marker='s', mfc='k', ms=8)
    line1, = pyplot.plot(hL, p)
    line2, = pyplot.plot(hV, p)
    pyplot.xlabel("h in [kJ/kg]")
    pyplot.ylabel("p in [bar]")
    pyplot.setp(line1, linewidth=2, color='b')
    pyplot.setp(line2, linewidth=2, color='r')
    pyplot.yscale('log')
    pyplot.grid()
    if path is None:
        pyplot.show()
    else:
        pyplot.savefig(path, bbox_inches='tight')


def demo_generate_Tp_diagramm():
    """Generate a T(p) Diagramm showing the Saturation Curve"""
    steam_table = XSteam(XSteam.UNIT_SYSTEM_MKS)
    p = np.arange(-100.0, 250.0, 1.0)
    ntsat_p = np.frompyfunc(steam_table.tsat_p, 1, 1)
    tsat = ntsat_p(p)
    line1, = pyplot.plot(tsat, p)
    pyplot.xlabel("t")
    pyplot.ylabel("p")
    pyplot.setp(line1, linewidth=1, color='b')
    pyplot.show()


def demo_generate_pvT_diagramm():
    """Generate a Diagramm showing the v(p,T) as a 3D survace"""
    steam_table = XSteam(XSteam.UNIT_SYSTEM_MKS)
    fig = pyplot.figure()
    ax = Axes3D(fig)
    p = np.arange(-10.0, 300.0, 5.0)
    t = np.arange(-50.0, 400.0, 5.0)
    p, t = np.meshgrid(p, t)
    npv_pt = np.frompyfunc(steam_table.v_pt, 2, 1)
    v = npv_pt(p, t)
    ax.plot_surface(v, p, t, rstride=1, cstride=1, linewidth=0, shade=True)
    ax.set_xlabel("v")
    ax.set_ylabel("p")
    ax.set_zlabel("t")
    pyplot.show()


def demo_moillier_diagramm():
    """Generate a moillier diagramm"""
    steam_table = XSteam(XSteam.UNIT_SYSTEM_MKS)
    s = np.arange(2.0, 10.0, 0.01)
    pSteps = [0.006117, 0.01, 0.02, 1.0, 2.0, 3.0, 10, 100, 1000]
    nph_ps = np.frompyfunc(steam_table.h_ps, 2, 1)
    for pstep in pSteps:
        h = nph_ps(pstep, s)
        hline, = pyplot.plot(s, h)
        pyplot.setp(hline, linewidth=1, color='b')
    pyplot.xlabel("s in [kJ/(kg K)]")
    pyplot.ylabel("h in [kJ/kg]")
    pyplot.show()


def demo_ice_diagramm():
    """Generate a diagram showing the sublimation and melting preasure"""
    steam_table = XSteam(XSteam.UNIT_SYSTEM_BARE)
    t_subl = np.arange(50.0, 273.16, 2.0)
    t_melt_Ih = np.arange(251.165, 273.16, 2.0)
    t_melt_III = np.arange(251.165, 256.164, 2.0)
    t_melt_V = np.arange(256.164, 273.31, 2.0)
    t_melt_VI = np.arange(273.31, 355.0, 2.0)
    t_melt_VII = np.arange(355.0, 751.0, 2.0)

    psubl_func = np.frompyfunc(steam_table.psubl_t, 1, 1)
    pmelt_func = np.frompyfunc(steam_table.pmelt_t, 2, 1)

    line1, = pyplot.plot(t_subl, psubl_func(t_subl))
    line2, = pyplot.plot(t_melt_Ih, pmelt_func(t_melt_Ih, steam_table.TYPE_ICE_Ih))
    line3, = pyplot.plot(t_melt_III, pmelt_func(t_melt_III, steam_table.TYPE_ICE_III))
    line4, = pyplot.plot(t_melt_V, pmelt_func(t_melt_V, steam_table.TYPE_ICE_V))
    line5, = pyplot.plot(t_melt_VI, pmelt_func(t_melt_VI, steam_table.TYPE_ICE_VI))
    line6, = pyplot.plot(t_melt_VII, pmelt_func(t_melt_VII, steam_table.TYPE_ICE_VII))

    pyplot.xlabel("T in [K]")
    pyplot.ylabel("p in [MPa]")
    pyplot.setp(line1, linewidth=1, color='b')
    pyplot.setp(line2, linewidth=1, color='g')
    pyplot.setp(line3, linewidth=1, color='r')
    pyplot.setp(line4, linewidth=1, color='y')
    pyplot.setp(line5, linewidth=1, color='g')
    pyplot.setp(line6, linewidth=1, color='r')
    pyplot.show()


def demo_simpel_values_heavy_water():
    """calculate values for heavy water and print the results"""
    steam_table_hw = XSteam_HW(XSteam_HW.UNIT_SYSTEM_MKS)
    print('my_rhoT(1.0, 320.0) =', steam_table_hw.my_rhoT(1.0, 320.0))
    print('my_rhoT(1.0, 320.0) =', steam_table_hw.tc_rhoT(1.0, 320.0))


if __name__ == '__main__':
    logger = logging.getLogger('pyXSteam')
    logger.setLevel(logging.DEBUG)
    sh = logging.StreamHandler()
    sh.setFormatter(logging.Formatter('%(name)s - %(levelname)s - %(message)s'))
    logger.addHandler(sh)

    print("Select which demo to run:")
    print("1. Run simple calculations")
    print("2. generate ph diagram")
    print("3. generate Tp diagram")
    print("4. generate pvT diagramm")
    print("5. generate moillier diagram")
    print("6. generate ice metling and sublimation diagram")
    print("7. Run sinple calculations for heavy water")

    selection = str(input("Please enter selection [1-7]: "))
    print("You selected " + selection)

    if selection == '1':
        start = time.process_time()
        demo_simpel_values()
        print("Demo took", time.process_time() - start, "seconds to complete")
    elif selection == '2':
        start = time.process_time()
        demo_generate_ph_diagramm()
        print("Demo took", time.process_time() - start, "seconds to complete")
    elif selection == '3':
        start = time.process_time()
        demo_generate_Tp_diagramm()
        print("Demo took", time.process_time() - start, "seconds to complete")
    elif selection == '4':
        start = time.process_time()
        demo_generate_pvT_diagramm()
        print("Demo took", time.process_time() - start, "seconds to complete")
    elif selection == '5':
        start = time.process_time()
        demo_moillier_diagramm()
        print("Demo took", time.process_time() - start, "seconds to complete")
    elif selection == '6':
        start = time.process_time()
        demo_ice_diagramm()
        print("Demo took", time.process_time() - start, "seconds to complete")
    elif selection == '7':
        start = time.process_time()
        demo_simpel_values_heavy_water()
        print("Demo took", time.process_time() - start, "seconds to complete")
    else:
        print("Unknown selection")

Indices and tables