flowtube.flow_calc

Conversion functions for flow rates and concentrations in flowtube package.

Functions

`Kn`(mean_free_path, char_length)	Calculate Knudsen number - eq.
`MR_to_molec`(obj, conc)	Convert mixing ratio in ppb to molecules cm-3.
`N_eff_Shw`(obj, length, FR)	Calculate the effective Sherwood number - eq.
`buoyancy_parameters`(obj, delta_T, distance, Re)	Calculate buoyancy parameters.
`ccm_to_sccm`(obj, FR)	Convert cm3 per min to sccm
`conductance`(obj, diameter, length)	Calculate conductance through cylinder - eq.
`length_to_laminar`(diameter, Re)	Entrance length (cm) - length to achieve laminar profile - Bird et al., 2002, page 52.
`mixing_time`(obj, diameter)	Calculate mixing time (s) - Hanson and Lovejoy, Geophys.
`molec_velocity`(obj, molar_mass)	Calculate thermal molecular velocity.
`pressure_gradient`(obj, conductance, FR)	Calculate pressure gradient - eqs.
`reynolds_number`(obj, FR, diameter)	Calculate Reynolds number for a gas flowing through a cylinder.
`reynolds_number_irregular`(obj, ...)	Calculate Reynolds number for a gas flowing through a cylinder.
`sccm_to_ccm`(obj, FR)	Convert sccm to cm3 per min.
`sccm_to_velocity`(obj, FR, diameter)	Calculate flow velocity.

Classes

`basic_attrs`(args, *kwargs)
`carrier_attrs`(args, *kwargs)
`full_attrs`(args, *kwargs)

class flowtube.flow_calc.basic_attrs(*args, **kwargs)[source]

P: float

T: float

__init__(*args, **kwargs)

class flowtube.flow_calc.carrier_attrs(*args, **kwargs)[source]

carrier_dynamic_viscosity: float

carrier_density: float

class flowtube.flow_calc.full_attrs(*args, **kwargs)[source]

reactant_diffusion_rate: float

reactant_molec_velocity: float

flowtube.flow_calc.sccm_to_ccm(obj, FR)[source]

Convert sccm to cm3 per min.

Parameters:

obj (basic_attrs) – Object with basic attributes (P in Pa, T in K).
FR (float) – Flow rate in sccm.

Returns:

Flow rate in cm3 min-1

Return type:

float

flowtube.flow_calc.ccm_to_sccm(obj, FR)[source]

Convert cm3 per min to sccm

Parameters:

obj (basic_attrs) – Object with basic attributes (P in Pa, T in K).
FR (float) – Flow rate in cm3 min-1.

Returns:

Flow rate to sccm.

Return type:

float

flowtube.flow_calc.sccm_to_velocity(obj, FR, diameter)[source]

Calculate flow velocity.

Parameters:

obj (basic_attrs) – Object with basic attributes (P in Pa, T in K).
FR (float) – Flow rate in sccm.
diameter (float) – Diameter in cm.

Returns:

Flow velocity in cm s-1.

Return type:

float

flowtube.flow_calc.MR_to_molec(obj, conc)[source]

Convert mixing ratio in ppb to molecules cm-3.

Parameters:

obj (basic_attrs) – Object with basic attributes (P in Pa, T in K).
conc (float) – Mixing ratio (ppb - mol mol-1).

Returns:

Concentration in molec. cm-3.

Return type:

float

flowtube.flow_calc.molec_velocity(obj, molar_mass)[source]

Calculate thermal molecular velocity. Formula matched to values from Knopf et al., Anal. Chem., 2015

Parameters:

obj (basic_attrs) – Object with basic attributes (P in Pa, T in K).
molar_mass (float) – Molar mass of the gas (g mol-1).

Returns:

Thermal molecular velocity in cm s-1.

Return type:

float

flowtube.flow_calc.reynolds_number(obj, FR, diameter)[source]

Calculate Reynolds number for a gas flowing through a cylinder.

Parameters:

obj (carrier_attrs) – Object with full attributes (P in Pa, T in K, carrier_dynamic_viscosity in kg m-1 s-1, carrier_density in kg m-3).
FR (float) – Total flow rate in sccm.
diameter (float) – Diameter of the cylinder (cm).

Returns:

Reynolds number.

Return type:

float

flowtube.flow_calc.reynolds_number_irregular(obj, cross_sectional_area, wetted_perimeter, FR)[source]

Calculate Reynolds number for a gas flowing through a cylinder. Formula 6-14 from Holman and Bhattacharyya 2011.

Parameters:

obj (carrier_attrs) – Object with full attributes (P in Pa, T in K, carrier_dynamic_viscosity in kg m-1 s-1, carrier_density in kg m-3).
cross_sectional_area (float) – Cross sectional area of the flow passage (cm2).
wetted_perimeter (float) – Wetted perimeter of the flow passage (cm).
FR (float) – Total flow rate in sccm.

Returns:

Reynolds number.

Return type:

float

flowtube.flow_calc.conductance(obj, diameter, length)[source]

Calculate conductance through cylinder - eq. 3.17 from Moore et al., 2009.

Parameters:

obj (carrier_attrs) – Object with full attributes (P in Pa, T in K, carrier_dynamic_viscosity in kg m-1 s-1, carrier_density in kg m-3).
diameter (float) – Inner diameter (cm).
length (float) – Length (cm).

Returns:

Conductance in L s-1.

Return type:

float

flowtube.flow_calc.pressure_gradient(obj, conductance, FR)[source]

Calculate pressure gradient - eqs. 3.9 & 3.10 from Moore et al., 2009.

Parameters:

obj (basic_attrs) – Object with basic attributes (P in Pa, T in K).
conductance (float) – Conductance in L s-1.
flow_rate (float) – Flow rate in sccm.
FR (float)

Returns:

Pressure gradient ratio.

Return type:

float

flowtube.flow_calc.buoyancy_parameters(obj, delta_T, distance, Re)[source]

Calculate buoyancy parameters.

Parameters:

obj (carrier_attrs) – Object with full attributes (P in Pa, T in K, carrier_dynamic_viscosity in kg m-1 s-1, carrier_density in kg m-3).
delta_T (float) – Temperature difference (K).
distance (float) – Distance over which the temperature difference is measured (cm) (typically axial or radial).
Re (float) – Reynolds number of the flow tube.

Returns:

Buoyancy parameter (>1 indicates the flow being driven by: buoyancy).

Return type:

float

flowtube.flow_calc.length_to_laminar(diameter, Re)[source]

Entrance length (cm) - length to achieve laminar profile - Bird et al., 2002, page 52. Note that the scalar term can vary depending on the source. Keyser, 1994 gives a value of 0.0565 for 99% attainment of parabolic profile while Hanson and Kosciuch, 2003 provide a value of 0.05 for 95% attainment. Using an exponential fit of the values, it seems that the 0.035 figure that Bird et al., 2002 gives is for a 85% attainment. Choose whichever value is most appropriate for your purposes.

Parameters:

diameter (float) – Diameter of the cylinder (cm).
Re (float) – Reynolds number of the flow tube.

Returns:

Length to laminar profile (cm).

Return type:

float

flowtube.flow_calc.mixing_time(obj, diameter)[source]

Calculate mixing time (s) - Hanson and Lovejoy, Geophys. Res. Lett., 1994.

Parameters:

obj (full_attrs) – Object with full attributes (P in Pa, T in K, reactant_diffusion_rate in cm2 s-1, carrier_dynamic_viscosity in kg m-1 s-1, carrier_density in kg m-3).
diameter (float) – Diameter of the cylinder (cm).

Returns:

Mixing time in seconds.

Return type:

float

flowtube.flow_calc.N_eff_Shw(obj, length, FR)[source]

Calculate the effective Sherwood number - eq. 11 from Knopf et al., 2015.

Parameters:

obj (full_attrs) – Object with full attributes (P in Pa, T in K, reactant_diffusion_rate in cm2 s-1, carrier_dynamic_viscosity in kg m-1 s-1, carrier_density in kg m-3).
length (float) – Length of the flow tube (cm).
FR (float) – Total flow rate in cm3 min-1.

Returns:

Effective Sherwood number.

Return type:

float

flowtube.flow_calc.Kn(mean_free_path, char_length)[source]

Calculate Knudsen number - eq. 8 from Knopf et al., 2015.

Parameters:

mean_free_path (float) – Mean free path of the reactant (cm).
char_length (float) – Characteristic length: diameter of cylinder for a coated wall reactor (cm).

Returns:

Knudsen number.

Return type:

float