exerpy.functions

exerpy.functions.add_chemical_exergy(my_json, Tamb, pamb, chemExLib)

Adds the chemical exergy to each connection in the JSON data, prioritizing molar composition if available.

Parameters: - my_json: The JSON object containing the components and connections. - Tamb: Ambient temperature in K. - pamb: Ambient pressure in Pa.

Returns: - The modified JSON object with added chemical exergy for each connection.

exerpy.functions.add_total_exergy_flow(my_json, split_physical_exergy)

Adds the total exergy flow to each connection in the JSON data based on its kind.

• For ‘material’ connections, the exergy is calculated as before.

• For ‘power’ connections, the energy flow value is used directly.

• For ‘heat’ connections, if the associated component is of class SimpleHeatExchanger, the thermal exergy difference is computed as:

  \[E = (e^\mathrm{T}_\mathrm{in} \cdot \dot m_\mathrm{in}) - (e^\mathrm{T}_\mathrm{out} \cdot \dot m_\mathrm{out})\]

Otherwise, a warning is logged and E is set to None.

Parameters:

• my_json (dict) – The JSON object containing the components and connections.

• split_physical_exergy (bool) – Split physical exergy in mechanical and thermal shares.

Returns:

dict – The modified JSON object with added total exergy flow for each connection.

exerpy.functions.calc_chemical_exergy(stream_data, Tamb, pamb, chemExLib)

Calculate the specific chemical exergy of a stream.

A pure substance gets the value of its reference phase. A pure substance without a value in the library gets 0, which is only valid if it does not react. A mixture is an ideal gas mixture. If water condenses at the ambient state, the liquid water forms a separate phase (Bejan et al., 1996, p. 138):

\[\bar{e}^\mathrm{CH} = x_\mathrm{g} \left( \sum_k y_k \bar{e}^\mathrm{CH}_k + \bar{R} T_0 \sum_k y_k \ln y_k \right) + x_\mathrm{H_2O,l} \, \bar{e}^\mathrm{CH}_\mathrm{H_2O,l}\]

with the molar fraction of the gas phase \(x_\mathrm{g}\) and the molar fractions \(y_k\) within the gas phase.

Parameters:

• stream_data (dict) – molar_composition or mass_composition of the stream.

• Tamb (float) – Ambient temperature in K.

• pamb (float) – Ambient pressure in Pa.

• chemExLib (str) – Name of the chemical exergy library, e.g. 'Ahrendts'.

Returns:

float – Specific chemical exergy in J/kg.

Raises:

ValueError – If the library has no value for a substance of a mixture.

exerpy.functions.mass_to_molar_fractions(mass_fractions)

Convert mass fractions to molar fractions.

Species with a zero mass fraction are left out. A stream of a single species gets the molar fraction 1 without its molar mass.

Parameters:

mass_fractions (dict) – Mass fractions by species name. The names have to be known to CoolProp.

Returns:

dict – Molar fractions by species name.

Raises:

ValueError – If CoolProp has no molar mass for a species with a nonzero mass fraction.

exerpy.functions.molar_to_mass_fractions(molar_fractions)

Convert molar fractions to mass fractions.

Parameters: - molar_fractions: Dictionary with component names as keys and molar fractions as values.

Returns: - mass_fractions: Dictionary with component names as keys and mass fractions as values.