# Permittivity/Dielectric Constant (thermo.permittivity)¶

This module contains implementations of TDependentProperty representing liquid permittivity. A variety of estimation and data methods are available as included in the chemicals library.

For reporting bugs, adding feature requests, or submitting pull requests, please use the GitHub issue tracker.

## Pure Liquid Permittivity¶

class thermo.permittivity.PermittivityLiquid(CASRN='', extrapolation='linear', **kwargs)[source]

Class for dealing with liquid permittivity as a function of temperature. Consists of one temperature-dependent simple expression, one constant value source, and IAPWS.

Parameters
CASRNstr, optional

The CAS number of the chemical

If False, do not load property coefficients from data sources in files [-]

extrapolationstr or None

None to not extrapolate; see TDependentProperty for a full list of all options, [-]

methodstr or None, optional

If specified, use this method by default and do not use the ranked sorting; an exception is raised if this is not a valid method for the provided inputs, [-]

Notes

To iterate over all methods, use the list stored in permittivity_methods.

CRC:

Simple polynomials for calculating permittivity over a specified temperature range only. The full expression is:

$\epsilon_r = A + BT + CT^2 + DT^3$

Not all chemicals use all terms; in fact, few do. Data is available for 759 liquids, from [1].

CRC_CONSTANT:

Constant permittivity values at specified temperatures only. Data is from [1], and is available for 1303 liquids.

IAPWS:

The IAPWS model for water permittivity as a liquid.

References

1(1,2)

Haynes, W.M., Thomas J. Bruno, and David R. Lide. CRC Handbook of Chemistry and Physics. [Boca Raton, FL]: CRC press, 2014.

Attributes
Tmax

Maximum temperature (K) at which the current method can calculate the property.

Tmin

Minimum temperature (K) at which the current method can calculate the property.

Methods

 calculate(T, method) Method to calculate permittivity of a liquid at temperature T with a given method. test_method_validity(T, method) Method to check the validity of a method.
property Tmax

Maximum temperature (K) at which the current method can calculate the property.

property Tmin

Minimum temperature (K) at which the current method can calculate the property.

calculate(T, method)[source]

Method to calculate permittivity of a liquid at temperature T with a given method.

This method has no exception handling; see T_dependent_property for that.

Parameters
Tfloat

Temperature at which to calculate relative permittivity, [K]

methodstr

Name of the method to use

Returns
epsilonfloat

Relative permittivity of the liquid at T, [-]

name = 'liquid relative permittivity'
property_max = 1000.0

Maximum valid of permittivity; highest in the data available is ~240.

property_min = 1.0

Relative permittivity must always be larger than 1; nothing is better than a vacuum.

ranked_methods = ['IAPWS', 'CRC', 'CRC_CONSTANT']

Default rankings of the available methods.

test_method_validity(T, method)[source]

Method to check the validity of a method. Follows the given ranges for all coefficient-based methods. For tabular data, extrapolation outside of the range is used if tabular_extrapolation_permitted is set; if it is, the extrapolation is considered valid for all temperatures.

It is not guaranteed that a method will work or give an accurate prediction simply because this method considers the method valid.

Parameters
Tfloat

Temperature at which to test the method, [K]

methodstr

Name of the method to test

Returns
validitybool

Whether or not a method is valid

units = '-'
thermo.permittivity.permittivity_methods = ['CRC', 'CRC_CONSTANT', 'IAPWS']

Holds all methods available for the PermittivityLiquid class, for use in iterating over them.