DETCHEM Channel Driver

This document describes the configuration directives that are available for use with the DETCHEM channel driver.

The DETCHEM Channel code simulates the steady state chemically reacting gas flow through either a cylindrical channel or an annular channel using the boundary layer approximation. Detailed mechanisms for surface and gas phase reactions are considered.

• Case of annular configuration:

  a=channel.radius.inner b=channel.radius.outer

  The reacting gas flows between the inner and outer pipe, therefore there are two surfaces, that can be
  catalytic active, which is described by the parameter catalytic_activity.inner and catalytic_activity.outer.

SI units are used exclusively throughout the program. Be sure to convert all values before importing data into CaRMeN. When referring to chemical species, use the correct capitalization, i.e. Ar instead of AR. Not doing so will lead to simulation errors since the species names will not be recognized.

Driver Name

This driver is available under the name detchem_channel.

Output Resources

This driver outputs two tabular data resources

• mole_fractions
• mass_fractions

Parameters

The following parameters are available.

# The pressure in the reactor (in this example: 0.5bar)
pressure: 0.5e5       # Pa      

# An object that defines the conditions of the gas flow entering the reactor,
# i.e. initial conditions
inlet:
  temperature: 429    # K
  gas_velocity: 0.47  # m/s
  # The composition of the gas entering the channel
  mole_fractions:
    CH4: 0.173
    O2: 0.19
    # An asterisk can be used to denote the remainder to unity.  It must be enclosed in quotes!
    N2: "*"           

# An object that defines the geometrical parameters of the channel
channel:
  length: 0.3         # m
  # The radius field can either be a number or an object.
  # A number defines a cylindrical channel configuration
  radius: 0.02        # m
  # An object with the fields inner and outer defines an annular channel
  # configuration (see image above). Here, the inner radius is set to 1.31cm
  # and the outer radius is set to 2.01cm.
  radius:
    inner: 1.31e-2    # m
    outer: 2.01e-2    # m

# The temperature of the channel wall. This field can be set to one of 3 types.
# The string "adiabatic" sets adiabatic conditions 
wall_temperature: adiabatic
# A number sets a constant wall temperature along the whole length  (isothermal conditions)
wall_temperature: 723 # K
# A variable temperature profile along channel length can also be set, typically using the
# $resource macro. In this case, the resource must be tabular data!
wall_temperature:
  $resource: ./temperature_profile.csv

# The ratio of catalytically active surface area and geometrical surface area.
f_cat_geo: 94.5       # dimensionless

# A complex object type describing the chemical model.
# Use the chemical-model loader to produce a resource with the correct structure,
# then access is using the $resource macro as shown here.
chemical_model:
  $resource: ./chemical_model


#
# Optional parameters follow below.
# The given values are the default values used when the parameter is omitted.
#

# An object describing the properties of the washcoat. Currently, only the effectiveness model
# is supported. Please file a feature request at https://gitlab.com/carmenjs/carmen/issues
# if you also need detailed washcoat models. The default is not to consider a washcoat model.
# Although the washcoat key itself is optional, the properties within the washcoat are not.
washcoat:
  thickness: 4e-5     # m  
  pore_diameter: 1e-8 # m
  tortuosity: 3       # dimensionless
  porosity: 0.6       # dimensionless
  # A list of diffusion limiting species used in the effectiveness factor model.
  diffusion_limiting_species:
    - CH4

# Defines the catalytic activity of channel walls. Useful in annular configurations.
catalytic_activity:
  # If set to true, surface reactions can occur on the inner wall of the channel.
  inner: false
  # If set to true, surface reactions can occur on the outer wall of the channel.
  outer: true

grid:
  # An integer that specifies the number of radial grid points.
  # Can be used to work around numerical issues.
  radial_points: 20

# Settings pertaining to the numerical solution.
# This driver currently does not support changing the solver tolerances!
# Please file a feature request at https://gitlab.com/carmenjs/carmen/issues
# if you need this feature.
solver:
  initial_integration_step_size: 1e-10
  max_integration_step_size: 1

# Settings for the solution of chemical source terms of surface reactions
chem_surf:
  initial_integration_step_size: 1e-10
  integration_time: 10.0
  max_integration_step_size: 1.0
  absolute_tolerance: 1e-20
  relative_tolerance: 1e-6