"""
Conversion functions for flow rates and concentrations in flowtube
package.
"""
from typing import Protocol
import numpy as np
from . import tools
[docs]
class basic_attrs(
Protocol,
):
P: float # Pressure in Pa
T: float # Temperature in K
[docs]
class carrier_attrs(
basic_attrs,
Protocol,
):
carrier_dynamic_viscosity: (
float # Dynamic viscosity of the carrier gas (kg m-1 s-1)
)
carrier_density: float # Density of the carrier gas (kg m-3)
[docs]
class full_attrs(
carrier_attrs,
Protocol,
):
reactant_diffusion_rate: float # Diffusion rate of the reactant (cm2 s-1)
reactant_molec_velocity: (
float # Thermal molecular velocity of the reactant (cm s-1)
)
### Flow rate conversion functions ###
[docs]
def sccm_to_ccm(
obj: basic_attrs,
FR: float,
) -> float:
"""Convert sccm to cm3 per min.
Args:
obj (basic_attrs): Object with basic attributes
(P in Pa, T in K).
FR (float): Flow rate in sccm.
Returns:
float: Flow rate in cm3 min-1
"""
return (
(tools.STANDARD_PRESSURE_Pa / obj.P) * obj.T / tools.STANDARD_TEMPERATURE_K * FR
)
[docs]
def ccm_to_sccm(
obj: basic_attrs,
FR: float,
) -> float:
"""Convert cm3 per min to sccm
Args:
obj (basic_attrs): Object with basic attributes
(P in Pa, T in K).
FR (float): Flow rate in cm3 min-1.
Returns:
float: Flow rate to sccm.
"""
return (
(obj.P / tools.STANDARD_PRESSURE_Pa) * tools.STANDARD_TEMPERATURE_K / obj.T * FR
)
[docs]
def sccm_to_velocity(
obj: basic_attrs,
FR: float,
diameter: float,
) -> float:
"""Calculate flow velocity.
Args:
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:
float: Flow velocity in cm s-1.
"""
return sccm_to_ccm(obj, FR) / tools.cross_sectional_area(diameter) / 60
### Physical calculations ###
[docs]
def MR_to_molec(
obj: basic_attrs,
conc: float,
) -> float:
"""Convert mixing ratio in ppb to molecules cm-3.
Args:
obj (basic_attrs): Object with basic attributes
(P in Pa, T in K).
conc (float): Mixing ratio (ppb - mol mol-1).
Returns:
float: Concentration in molec. cm-3.
"""
return (
obj.P
/ (tools.UNIVERSAL_GAS_CONSTANT * obj.T)
* tools.AVOGADROS_NUMBER
/ 100**3
* conc
* 1e-9
)
[docs]
def molec_velocity(
obj: basic_attrs,
molar_mass: float,
) -> float:
"""
Calculate thermal molecular velocity. Formula matched to values from
Knopf et al., Anal. Chem., 2015
Args:
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:
float: Thermal molecular velocity in cm s-1.
"""
return 100 * np.sqrt(
8 / np.pi * tools.UNIVERSAL_GAS_CONSTANT * obj.T / molar_mass * 1000
)
### Flow diagnostics calculations ###
[docs]
def reynolds_number(
obj: carrier_attrs,
FR: float,
diameter: float,
) -> float:
"""Calculate Reynolds number for a gas flowing through a cylinder.
Args:
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:
float: Reynolds number.
"""
return (
(obj.carrier_density / 100**3)
* sccm_to_velocity(obj, FR, diameter)
* diameter
/ (obj.carrier_dynamic_viscosity / 100)
)
[docs]
def reynolds_number_irregular(
obj: carrier_attrs,
cross_sectional_area: float,
wetted_perimeter: float,
FR: float,
) -> float:
"""
Calculate Reynolds number for a gas flowing through a cylinder.
Formula 6-14 from Holman and Bhattacharyya 2011.
Args:
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:
float: Reynolds number.
"""
hydraulic_diameter = 4 * cross_sectional_area / wetted_perimeter
return (
(obj.carrier_density / 100**3)
* sccm_to_ccm(obj, FR)
/ cross_sectional_area
/ 60
* hydraulic_diameter
/ (obj.carrier_dynamic_viscosity / 100)
)
[docs]
def conductance(
obj: carrier_attrs,
diameter: float,
length: float,
) -> float:
"""
Calculate conductance through cylinder - eq. 3.17 from Moore et al.,
2009.
Args:
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:
float: Conductance in L s-1.
"""
return (
32600
* diameter**4
/ (obj.carrier_dynamic_viscosity * 1e7 * length)
* obj.P
/ tools.P_CF["Torr"]
)
[docs]
def pressure_gradient(
obj: basic_attrs,
conductance: float,
FR: float,
) -> float:
"""
Calculate pressure gradient - eqs. 3.9 & 3.10 from Moore et al.,
2009.
Args:
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.
Returns:
float: Pressure gradient ratio.
"""
return sccm_to_ccm(obj, FR) / 60 / 1000 / conductance
[docs]
def buoyancy_parameters(
obj: carrier_attrs,
delta_T: float,
distance: float,
Re: float,
) -> float:
"""Calculate buoyancy parameters.
Args:
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:
float: Buoyancy parameter (>1 indicates the flow being driven by
buoyancy).
"""
# Grashof Number - eq. 9.12 from Incropera, et al., 2007
grashof_number = (
9.81
/ obj.T
* delta_T
* distance**3
/ (obj.carrier_dynamic_viscosity / 100 / (obj.carrier_density / 100**3)) ** 2
)
return grashof_number / Re**2
[docs]
def length_to_laminar(
diameter: float,
Re: float,
) -> float:
"""
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.
Args:
diameter (float): Diameter of the cylinder (cm).
Re (float): Reynolds number of the flow tube.
Returns:
float: Length to laminar profile (cm).
"""
return 0.05 * diameter * Re
[docs]
def mixing_time(
obj: full_attrs,
diameter: float,
) -> float:
"""
Calculate mixing time (s) - Hanson and Lovejoy, Geophys. Res. Lett.,
1994.
Args:
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:
float: Mixing time in seconds.
"""
return (diameter / 2) ** 2 / (5 * obj.reactant_diffusion_rate)
### KPS Method Calculations ###
[docs]
def N_eff_Shw(
obj: full_attrs,
length: float,
FR: float,
) -> float:
"""
Calculate the effective Sherwood number - eq. 11 from Knopf et al.,
2015.
Args:
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:
float: Effective Sherwood number.
"""
# Axial Distance (unitless)
# - eq. 2 from Knopf et al., Anal. Chem., 2015
z_star = (
length * np.pi / 2 * obj.reactant_diffusion_rate / (sccm_to_ccm(obj, FR) / 60)
)
return 3.6568 + 0.0978 / (z_star + 0.0154)
[docs]
def Kn(
mean_free_path: float,
char_length: float,
) -> float:
"""Calculate Knudsen number - eq. 8 from Knopf et al., 2015.
Args:
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:
float: Knudsen number.
"""
return 2 * mean_free_path / char_length
"""
Citations:
Bird, R.B., Stewart, W.E., Lightfoot, E.N., 2002. Transport phenomena,
2nd, Wiley international ed ed. J. Wiley, New York.
Knopf, D.A., Pöschl, U., Shiraiwa, M., 2015. Radial Diffusion and
Penetration of Gas Molecules and Aerosol Particles through Laminar Flow
Reactors, Denuders, and Sampling Tubes. Anal. Chem. 87, 3746–3754.
https://doi.org/10.1021/ac5042395
Keyser, L.F., 1984. High-pressure flow kinetics. A study of the hydroxyl
+ hydrogen chloride reaction from 2 to 100 torr. J. Phys. Chem. 88,
4750–4758. https://doi.org/10.1021/j150664a061
Hanson, D.R., Lovejoy, E.R., 1994. The uptake of N2O5 onto small
sulfuric acid particles. Geophys. Res. Lett. 21, 2401–2404.
https://doi.org/10.1029/94GL02288
Holman, J. P., & Bhattacharyya, S. (2011). Heat transfer in SI units
(10th ed.). McGraw-Hill. p. 284
Moore, J.H., Davis, C.C., Coplan, M.A., 2009. Building Scientific
Apparatus, 4th ed. ed. Cambridge University Press, Leiden.
Incropera, F.P., DeWitt, D.P., Bergman, T.L., Lavine, A.S. (Eds.), 2007.
Fundamentals of heat and mass transfer, 6. ed. ed. Wiley, Hoboken, NJ.
"""