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.

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Pure Liquid Permittivity

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

Bases: TDependentProperty

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

load_databool, optional

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, [-]

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 test the validity of a specified method for a given temperature.

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_PERMITTIVITY:

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.

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)

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_PERMITTIVITY', 'CRC', 'CRC_CONSTANT']

Default rankings of the available methods.

test_method_validity(T, method)

Method to test the validity of a specified method for a given temperature. Demo function for testing only; must be implemented according to the methods available for each individual method. Include the interpolation check here.

Parameters:

Tfloat

Temperature at which to determine the validity of the method, [K]

methodstr

Method name to use

Returns:

validitybool

Whether or not a specifid method is valid

units = '-'

thermo.permittivity.permittivity_methods = ['CRC', 'CRC_CONSTANT', 'IAPWS_PERMITTIVITY']

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