z-units

A simple unit-converter for chemical engineers

Feature

• Gauge pressure units (MPag, kPag, psig, ...) are ready for use
• Friendly to HYSYS user

Install

pip install z-units

Quickstart

>>> from zunits 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 zunits import convert
>>> convert(1, 'm', 'ft')
<Length(3.2808399, 'ft')>

Related to gauge pressure, local atmospheric pressure (default: 101325 Pa) can be altered:

>>> from zunits import config
# Before
>>> q.Pressure(100, 'kPa').to('kPag')
<Pressure(-1.325, 'kPag')>
# Set to 50e3 Pa (50 kPa)
>>> config.set_local_atmospheric_pressure(50e3)
# After
>>> q.Pressure(100, 'kPa').to('kPag')
<Pressure(50.0, 'kPag')>

Standard temperature (default: 20 degC) can be redefined, affecting standard cubic meter "Sm**3":

# Before
>>> q.Substance(100, 'Nm3').to('Sm3')
<Substance(107.321984, 'Sm3')>
# Set to 15 degC
>>> config.set_standard_temperature(15)
# After
>>> q.Substance(100, 'Nm3').to('Sm3')
<Substance(105.491488, 'Sm3')>

Format quantity to string with styles:

# Only value
>>> format(q.MolarEntropy(100))
'100'
# With unit, quick style
>>> format(q.MolarEntropy(100), 'u')
'100 kJ/kmol-C'
# With unit, definition style
>>> format(q.MolarEntropy(100), 'up')
'100 kJ/(kmol*C)'

Predefined Quantities

• Length
• Area
• Volume
• Time
• Mass
• Force
• Substance
• Energy
• Velocity
• Temperature
• DeltaTemperature
• Pressure
• VolumeFlow
• MassDensity
• HeatFlow
• MolarFlow
• MassFlow
• MolarDensity
• MolarHeatCapacity
• MolarEntropy
• MolarHeat
• ThermalConductivity
• Viscosity
• SurfaceTension
• MassHeatCapacity
• MassEntropy
• MassHeat
• StandardGasFlow
• KinematicViscosity
• MolarVolume
• Fraction
• Dimensionless

About it

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.