Source code for RCAIDE.Library.Attributes.Gases.Steam
# RCAIDE/Library/Attributes/Gases/CO2.py
#
#
# Created: Mar 2024, M. Clarke
# ----------------------------------------------------------------------------------------------------------------------
# Imports
# ----------------------------------------------------------------------------------------------------------------------
from .Gas import Gas
# ----------------------------------------------------------------------------------------------------------------------
# Steam Class
# ----------------------------------------------------------------------------------------------------------------------
[docs]
class Steam(Gas):
"""
A class representing water vapor (steam) and its thermodynamic properties. Provides methods for computing
various gas properties including density, speed of sound, and specific heat.
Attributes
----------
tag : str
Identifier for the gas type ('steam')
molecular_mass : float
Molecular mass of H2O in kg/kmol (18.0)
gas_specific_constant : float
Specific gas constant in m²/s²-K (461.889)
composition : Data
Chemical composition of steam
- H2O : float
Mass fraction of water vapor (1.0)
Notes
-----
This class implements steam properties assuming ideal gas behavior for most calculations.
All properties are for pure water vapor.
"""
def __defaults__(self):
"""This sets the default values.
Assumptions:
None
Source:
None
"""
self.tag ='steam'
self.molecular_mass = 18. # kg/kmol
self.gas_specific_constant = 461.889 # m^2/s^2-K, specific gas constant
self.composition.H2O = 1.0
[docs]
def compute_density(self,T=300,p=101325):
"""
Computes steam density using the ideal gas law.
Parameters
----------
T : float
Temperature in Kelvin
p : float
Pressure in Pascal
Returns
-------
rho : float
Density in kg/m³
Notes
-----
**Major Assumptions**
* Steam behaves as an ideal gas
"""
return p/(self.gas_specific_constant*T)
[docs]
def compute_speed_of_sound(self,T=300,p=101325,variable_gamma=False):
"""
Computes speed of sound in steam.
Parameters
----------
T : float
Temperature in Kelvin
p : float
Pressure in Pascal
variable_gamma : bool
If True, uses temperature-dependent specific heat ratio
Returns
-------
a : float
Speed of sound in m/s
Notes
-----
**Major Assumptions**
* If variable_gamma is False, assumes γ = 1.33
* Steam behaves as an ideal gas
"""
if variable_gamma:
g = self.compute_gamma(T,p)
else:
g = 1.33
return (g*self.gas_specific_constant*T)**0.5
[docs]
def compute_cp(self,T=300,p=101325):
"""
Computes specific heat capacity at constant pressure using a 3rd-order polynomial fit.
Parameters
----------
T : float
Temperature in Kelvin
p : float
Pressure in Pascal
Returns
-------
cp : float
Specific heat capacity in J/(kg·K)
Notes
-----
**Major Assumptions**
* Valid for temperature range: 300 K < T < 1500 K
**Theory**
.. math::
c_p(T) = c_1T^3 + c_2T^2 + c_3T + c_4
References
----------
[1] Carvalho, M. G., Lockwood, F. C., Fiveland, W. A., & Papadopoulos, C. (2022). Combustion Technologies for a clean environment: Selected papers from the proceedings of the first international conference, Vilamoura, Portugal, September 3-6, 1991. CRC Press.
"""
c = [5E-9, -.0001, .9202, 1524.7]
cp = c[0]*T**3 + c[1]*T**2 + c[2]*T + c[3]
return cp
[docs]
def compute_gamma(self,T=300,p=101325):
"""
Returns the specific heat ratio for steam.
Parameters
----------
T : float
Temperature in Kelvin
p : float
Pressure in Pascal
Returns
-------
g : float
Specific heat ratio (gamma) [unitless]
Notes
-----
**Major Assumptions**
* Valid for temperature range: 233 K < T < 1273 K
* Uses constant value of 1.33
"""
g = 1.33
return g
[docs]
def compute_absolute_viscosity(self,T=300,p=101325):
"""
Returns the absolute (dynamic) viscosity of steam.
Parameters
----------
T : float
Temperature in Kelvin
p : float
Pressure in Pascal
Returns
-------
mu : float
Absolute viscosity in kg/(m·s)
Notes
-----
**Major Assumptions**
* Uses constant value of 1e-6 kg/(m·s)
"""
mu =1E-6
return mu
