Quick Start Guide

This guide will get you up and running with sandlersteam in just a few minutes.

Basic Concepts

sandlersteam provides implementations of steam-table lookups from tables in Appendix III of Sandler’s textbook. These tables report temperatures in °C and pressures in either kPa or MPa. Queries can be made using any two independent state variables, such as temperature and pressure, or temperature and specific volume. The following properties are returned:

  • Specific enthalpy (h), entropy (s), volume (v), and internal energy (u)

  • Vapor fraction (xvap) for two-phase states

Temperature is in °C and pressure is in megapascals (MPa) by default.

Note that sandlersteam represents all dimensioned properties using pint.Quantity objects, so you can easily convert between different units in the API.

First Calculation

Let’s calculate the molar volume of methane at 400 K and 0.5 MPa using the Peng-Robinson equation:

From the Command Line

Unsaturated steam/water state calculations:

sandlersteam state -T 400 -P 1.1

Output:

T =   400 degree_Celsius
P =   1.1 megapascal
v =  0.2807 meter ** 3 / kilogram
u =  2956.1 kilojoule / kilogram
h =  3262.3 kilojoule / kilogram
s =  7.42125 kilojoule / kelvin / kilogram

Saturated steam/water state calculations:

sandlersteam state -P 4.0 -x 0.9

Output:

T  =  250.4 degree_Celsius
P  =     4 megapascal
v  =  0.0449272 meter ** 3 / kilogram
u  =  2450.3 kilojoule / kilogram
h  =  2629.99 kilojoule / kilogram
s  =  5.74273 kilojoule / kelvin / kilogram
x  = 0.9 dimensionless
vL =  0.001252 meter ** 3 / kilogram
uL =  1082.31 kilojoule / kilogram
hL =  1087.31 kilojoule / kilogram
sL =  2.7964 kilojoule / kelvin / kilogram
vV =  0.04978 meter ** 3 / kilogram
uV =  2602.3 kilojoule / kilogram
hV =  2801.4 kilojoule / kilogram
sV =  6.0701 kilojoule / kelvin / kilogram

From Python

from sandlersteam.state import State
state1 = State(T=200.0, P=0.1)

print(f"Specific volume: {state1.v}")

When using the API, note that you can use dot notation to access properties directly, and to reset the initial inputs. For example:

from sandlersteam.state import State
state = State(T=200.0, P=0.1)

print(f"Specific volume: {state.v}")

# Change state to new conditions
state.T = 300.0  # this will fully specify the state and recalculate all properties, at T=300 C and previous P=0.1 MPa
print(f"New specific volume: {state.v}")

state.P = 0.5 # this will fully specify the state and recalculate all properties at P=0.5 MPa and previous T=300 C
print(f"Another new specific volume: {state.v}")

If you use dot notation to overwrite a property that is not a state’s input property, this will wipe out the existing inputs and you will need to set one more independent property to fully specify the state. For example:

from sandlersteam.state import State
state = State(T=200.0, P=0.1)

print(f"Specific volume: {state.v}") # it is 2.172 m^3/kg

# Overwrite a property that is not an input
state.v = 5.5  # this will wipe out previous T and P inputs; state is now underspecified

# Need to set one more independent property again
state.P = 0.1  # now state is fully specified again at P=0.1 MPa and v=5.5 m^3/kg

print(f"New state temperature: {state.T}") # it will be a little over 918.6 C

You can initialize a state with no inputs, then set any two independent properties later:

from sandlersteam.state import State
state = State()  # no inputs yet

state.T = 150.0  # set temperature
state.P = 0.2    # set pressure, now state is fully specified

print(f"Specific volume: {state.v}") # it will be 0.9596 m^3/kg

The attributes you can set using dot notation are:

  • T : Temperature (°C)

  • P : Pressure (MPa)

  • v : Specific volume (m³/kg)

  • u : Specific internal energy (kJ/kg)

  • h : Specific enthalpy (kJ/kg)

  • s : Specific entropy (kJ/(kg K))

  • x : Vapor mass fraction (0 to 1 for two-phase states)

  • name : just a label for the state (string)

State-Change Calculations

Calculate property changes between two thermodynamic states:

From the Command Line

sandlersteam delta -P1 4.0 -T1 800 -P2 4.5 -T2 1200 --show-states

Output:

State-change calculations for Steam:

State 1:                                      State 2:
T =   800 degree_Celsius                      T =  1200 degree_Celsius
P =     4 megapascal                          P =   4.5 megapascal
v =  0.12287 meter ** 3 / kilogram            v =  0.15098 meter ** 3 / kilogram
u =   3650 kilojoule / kilogram               u =  4457.5 kilojoule / kilogram
h =  4141.5 kilojoule / kilogram              h =  5136.9 kilojoule / kilogram
s =  7.8502 kilojoule / kelvin / kilogram     s =  8.5825 kilojoule / kelvin / kilogram

Property changes:
ΔT  =    400 delta_degree_Celsius
ΔP  =    0.5 megapascal
Δv  =  0.02811 meter ** 3 / kilogram
Δu  =  807.5 kilojoule / kilogram
Δh  =  995.4 kilojoule / kilogram
Δs  =  0.7323 kilojoule / kelvin / kilogram

From Python

State-change calculations can be performed by creating two State objects representing the initial and final states, then using the built-in delta() method to compute property differences:

from sandlersteam.state import State

# State 1
state1 = State(T=350, P=7.5)

# State 2
state2 = State(T=400, P=15.5)

# Calculate property differences using built-in methods
deltas = state1.delta(state2)

print(f"Δh = {deltas['h']:7g}")
print(f"Δs = {deltas['s']:7g}")
print(f"Δu = {deltas['u']:7g}")

Next Steps