z-units 0.2.1

A simple unit converter for chemical engineers

z-units

A simple unit-converter for chemical engineers

Features

• Gauge pressure units (MPag, kPag, psig, ...) with configurable atmospheric pressure
• Standard volume units (Sm³) with configurable STP conditions
• Friendly to HYSYS users
• Rich formatting options

Installation

pip install z-units

Quickstart

>>> from z_units import quantity as q
>>> f = q.MolarFlow(3)
>>> f
<MolarFlow(3, 'kmol/s')>
>>> f.value, f.unit
(3, <Unit('kmol/s')>)
>>> f.to('kmol/h')
<MolarFlow(10800.0, 'kmol/h')>
>>> q.Length(100, 'cm') == q.Length(1000, 'mm')
True
>>> q.Temperature('100C')
<Temperature(1, 'C')>
>>> q.Pressure(15, 'psi').to('MPag')
<Pressure(0.0020963594, 'MPag')>
>>> from z_units import convert
>>> convert(1, 'm', 'ft')
<Length(3.2808399, 'ft')>

Advanced Features

Gauge Pressure Handling

The atmospheric pressure reference (default: 101325 Pa) can be configured globally or passed as an argument locally.

Using argument locally:

>>> q.Pressure(100, 'kPa', atm_pressure=50e3).to('kPag')
<Pressure(50.0, 'kPag')>
>>> q.Pressure(100, 'kPa').to('kPag', atm_pressure=50e3)
<Pressure(50.0, 'kPag')>

Using global configuration:

>>> from z_units.environment import get_env
# Before
>>> q.Pressure(100, 'kPa').to('kPag')
<Pressure(-1.325, 'kPag')>
# Set to 100 kPa
# atmospheric_pressure in Pa
>>> env = get_env()
>>> env.atmospheric_pressure = 100e3
# After
>>> q.Pressure(100, 'kPa').to('kPag')
<Pressure(0.0, 'kPag')>

Standard Volume Units

Standard temperature and pressure (STP) conditions can be configured for standard volume conversions:

>>> from z_units.environment import get_env
# Default STP: 20°C, 101325 Pa
>>> q.Substance(100, 'Nm3').to('Sm3')
<Substance(107.321984, 'Sm3')>
# Change to 15°C, set value in K
>> > get_env().standard_temperature = 273.15 + 15
>> > q.Substance(100, 'Nm3').to('Sm3')
<Substance(105.491488, 'Sm3')>

Unit Formatting

Multiple formatting styles are supported:

>>> x = q.MolarEntropy(100)
# Only value
>>> f"{x}"
'100'
# Quick style (simplified)
>>> f"{x:q}"
'100 kJ/kmol-C'
# Python style (full)
>>> f"{x:p}"
'100 kJ/(kmol*C)'

Predefined Quantities

• Length (m, km, cm, mm, ft, in, ...)
• Area (m2, km2, ...)
• Volume (m3, L, mL, ...)
• Time (s, min, h, ...)
• Mass (kg, g, lb, ...)
• Force (N, kN, ...)
• Substance (mol, kmol, ...)
• Energy (J, kJ, kWh, ...)
• Velocity (m/s, km/h, ...)
• Temperature (K, C, F)
• DeltaTemperature (K, C, F)
• Pressure (Pa, kPa, kPag, MPa, MPag, bar, barg, psi, psig...)
• VolumeFlow (m³/s, L/min, ...)
• StandardGasFlow (Nm3/h, Sm3/h, ...)
• MolarFlow (mol/s, kmol/h, ...)
• MassFlow (kg/s, t/h, ...)
• Density (kg/m3, g/cm3, ...)
• MolarDensity (mol/m3, kmol/m3)
• HeatCapacity (J/kg-K, kJ/kg-K)
• MolarHeatCapacity (J/mol-K, kJ/kmol-K))
• Entropy (J/kg-K), kJ/kg-K)
• MolarEntropy (J/mol-K, kJ/kmol-K)
• ThermalConductivity (W/m-K)
• Viscosity (Pa-s, cP)
• KinematicViscosity (m2/s, cSt)
• SurfaceTension (N/m)
• Dimensionless

Environment Configuration

Global environment parameters can be configured:

>>> from z_units.environment import get_env
# Set atmospheric pressure
>>> get_env().atmospheric_pressure = 100e3  # 100 kPa
# Set standard conditions
>>> get_env().standard_temperature = 273.15  # 0°C
>>> get_env().standard_pressure = 101325  # 1 atm
# Reset to defaults
>>> get_env().reset()

About

As a chemical engineer, the Gauge-Pressure units are very useful to me. Unfortunately those units are not supported in some popular modules, so I reinvent the wheel.

License

MIT License