Reacting Channel Co-Simulation Reference

Reacting channel co-simulation occurs between a 3D domain in Simcenter STAR-CCM+ and reacting channels that use a 1D Plug Flow Reactor (PFR).

You can use the Reacting Channel co-simulation model in Simcenter STAR-CCM+ to solve reacting flow simulations in tubular heat exchangers with channels that are long and thin.

This functionality is useful for simulating chemical processes such as steam reforming which occurs within narrow tubes surrounded by a firebox that is heated by combustion.

Table 1. Reacting Channel Model Reference
Theory	See Reacting Channel Coupling.
Provided By	[physics continuum] > Models > Co-Simulation Models
Example Node Path	Continua > Physics 1 > Models > Reacting Channel
Requires	One of the following combinations of model selections:
	When reactions occur in the fluid that surrounds the reacting channels: Material: Multi-Component Gas or Multi-Component Liquid Reaction Regime: Reacting Reacting Flow Models: any Additional combustion/turbulence models, as required. Flow: any Space: Three Dimensional Time: Steady Enthalpy: any Optional Models: Co-Simulation		When there are no reactions within the fluid that surrounds the reacting channels: Material: Multi-Component Gas, Multi-Component Liquid, Gas, or Liquid (when Multi-Component Gas or Multi-Component Liquid are selected: Reaction Regime: Non-Reacting) Flow: any Space: Three Dimensional Time: Steady (Equation of State: any) Energy: any Optional Models: Co-Simulation
Activates	Physics Models	Reacting Channel Coupling Models
	Model Controls	When the Reacting Channel model is selected, an External Links > Reacting Channel Co-Simulation node is added to the simulation object tree. The Reacting Channel Co-Simulation node contains four sub-nodes which allow you to define the reacting channel: Models, Zones, Conditions, and Values.
	Reports	Combustion > Reacting Channel Outlet Quantity. See Reports.
	Reference Values	Minimum Allowable Temperature, Maximum Allowable Temperature. See Reference Values.
	Boundary Inputs	External Code Coupling Specification. See Boundary Settings.

Models

Link models configure the connection to a partner application or file. The link icon changes based on the application, or file, that Simcenter STAR-CCM+ connects to through the link. The link model must be appropriate for the co-simulation or file export model selected in the physics continuum.

For reacting channel co-simulations, the Reacting Channel model is selected and cannot be modified.

Zones

The Zones node contains a [Zone n] node for each zone that you specify. Each [Zone n] node contains two additional sub-nodes in which you specify the Conditions and Values of that specific zone.

Zones > [Zone n] > Conditions

Coupled Model Parts

Boundaries: Displays a read only value which contains the boundaries that are specified for that reacting channel zone.
Regions: Displays a read only value which contains the regions that are specified for that reacting channel zone.

Equation of State (EOS) Option

Equation of State (EOS) Type

EOS Type	Corresponding Values Node
Ideal Gas The fluid within the reacting channels follows the ideal gas law. This option is intended for modeling gas-filled reacting channels.
Constant The mixture density in the reacting channels is calculated as a mass fraction weighted sum of the individual species densities, which are specified as constant. This option is intended for modeling liquid-filled reacting channels.	Component Densities Allows you to define a constant density value for each species in the fluid. By default, if a species is contained in the material database, the constant densities are set to those of the material database.

EOS Type

Corresponding Values Node

Ideal Gas

The fluid within the reacting channels follows the ideal gas law. This option is intended for modeling gas-filled reacting channels.

Constant

The mixture density in the reacting channels is calculated as a mass fraction weighted sum of the individual species densities, which are specified as constant.

This option is intended for modeling liquid-filled reacting channels.

Component Densities

Allows you to define a constant density value for each species in the fluid. By default, if a species is contained in the material database, the constant densities are set to those of the material database.

Heat Transfer Coefficient Correlation

Only available when Reacting Channel Inlet Type is set to Specified Inlet and Reacting Channel Type is set to Packed Bed.

Correlation Type

Allows you to specify the correlation type for the heat transfer coefficient:

Leva/Grummer
Determines the heat transfer coefficient using Eqn. (3817)
Beek
Determines the heat transfer coefficient using Eqn. (3819)
DeWasch/Froment
Determines the heat transfer coefficient using Eqn. (3820)

Pipe Friction Correlation

Only available when Reacting Channel Inlet Type is set to Specified Inlet.

Correlation Type

Allows you to specify the correlation type for the pipe friction coefficient

Blasius (Pipe)
Determines the pipe friction coefficient using Eqn. (3821)
Filonenko (Pipe)
Determines the pipe friction coefficient using Eqn. (3822)
Ergun (Packed Bed)
Determines the pipe friction coefficient using Eqn. (3824) which is valid for simulations with low $\frac{Re}{1 - χ}$ values.
Hicks (Packed Bed)
Determines the pipe friction coefficient using Eqn. (3823) which is valid for simulations with high $\frac{Re}{1 - χ}$ values.
Ergun/Hicks (Packed Bed)
Determines the pipe friction coefficient using Ergun correlation (Eqn. (3824)) when $\frac{Re}{1 - χ} < 300$ , Hicks correlation (Eqn. (3823)) when $\frac{Re}{1 - χ} > 500$ , and linear interpolation in between.

Reacting Channel Area Option

Only available when Reacting Channel Inlet Type is set to Specified Inlet.

Allows you to specify the cross-sectional area of one geometrical channel in a reacting channel zone (each geometrical channel within a reacting channel zone is expected to be of equivalent dimensions).

Reacting Channel Area Option

Sets the method for defining the channel cross-sectional area which is used to compute the diameter

D_{C}

for the convective heat transfer coefficient of the reacting channel,

h_{f}

in Eqn. (3813).

Constant
Allows you to specify the Reacting Channel Area as a constant value.
Tabular
Adds a Values > Area node which allows you to specify the channel cross-sectional area as a function of channel distance using imported tabular data.

Reacting Channel Heat Transfer Coefficient Option

Only available when Reacting Channel Inlet Type is set to Specified Inlet.

Reacting Channel Heat Transfer Coefficient Option

Allows you to specify the method for determining the Heat Transfer Coefficient,

h_{f}

which is used to determine the convective heat transfer source

{\dot{Q}}_{C}

in Eqn. (3812).

Constant
Adds a Values > Heat Transfer Coefficient node which allows you to specify the Heat Transfer Coefficient, $h_{f}$ as a constant array value.
Uniform
Allows you to specify the Heat Transfer Coefficient using values which are taken directly from the reacting channel Inlet values.
Non-Uniform
Determines the heat transfer coefficient using data from each axial point.
Tabular
Adds a Values > Heat Transfer Coefficient node which allows you to specify the Heat Transfer Coefficient using tabular data which you can import.

Reacting Channel Inlet Type

Inlet Type

Specified Inlet
Allows you to specify which boundaries of the reacting channels are the inlet boundaries. The inlet and outlet boundaries are not connected.
Re-Entry
Simulates uninterrupted flow from one reacting channel into another by allowing Simcenter STAR-CCM+ to account for joined-up channels by means of a virtual U-bend. Provides the Values > Re-Entry Boundaries which you use to specify the boundaries that are concurrent. Also provides the Orientation property under the Values > Wall Discretization node which you use to specify the orientation of the channels in each zone.

Reacting Channel Inlet Viscosity Option

Only available when Reacting Channel Inlet Type is set to Specified Inlet.

Option

Allows you to specify how the viscosity,

μ

, of the components entering the reacting channel is determined at the reacting channel inlet:

Constant
Adds a Values > Inlet Viscosity node which allows you to set a value for the gas Viscosity at the inlet.
Uniform
Allows you to specify the gas Viscosity at the inlet using values which are taken directly from the reacting channel Inlet values.

Reacting Channel Pipe Friction Factor Option

Only available when Reacting Channel Inlet Type is set to Specified Inlet.

Option

Allows you to specify a multiplying factor for the pipe friction,

f

which is used to calculate the Nusselt number Eqn. (3815) for cases with turbulent flow. It is also used to calculate pressure drop in Eqn. (3825).

Constant
Allows you to specify a constant value for the Values > Pipe Friction Factor node.
Tabular
Allows you to specify the Values > Pipe Friction Factor using tabular data that you can import.

Reacting Channel Type

Only available when Reacting Channel Inlet Type is set to Specified Inlet.

Correlation Type

Allows you to specify the correlation type for the reacting channel:

Pipe
Specifies the pipes as empty reacting channels – which contain no material other than the gas that is in them.
Packed Bed
Specifies the pipes as fixed bed / packed bed reacting channels. This option is suitable for modeling applications such as steam cracking and methane steam reforming.

Reacting Channel Wall Temperature Option

Only available when Reacting Channel Inlet Type is set to Specified Inlet.

Option

Allows you specify how the Reacting Channel Wall Temperature

T_{W}

, Eqn. (3812), is determined at the wall boundary:

Uniform
Determines the temperature using data that is averaged from all axial points throughout the reacting channel zone.
Non-Uniform
Determines the temperature using data from each axial point throughout the reacting channel zone.

Thermal Conductivity/Dynamic Viscosity Method

Thermal Conductivity/Dynamic Viscosity Method

Kinetic Theory
Constant

Zones > [Zone n] > Values

The following Values are available to specify for each reacting channel zone:

Component Dynamic Viscosities

Available to specify when Thermal Conductivity/Dynamic Viscosity Method is set to Constant.

Allows you to specify the constant dynamic viscosities,

μ

in Eqn. (3816), of the components entering the reacting channel inlet.

Component Thermal Conductivities

Available to specify when Thermal Conductivity/Dynamic Viscosity Method is set to Constant.

Allows you to specify the constant thermal conductivities of the components entering the reacting channel inlet.

Area

Allow you to specify the reacting channel area using the following options:

As a constant value when Reacting Channel Area Option is set to Constant
As tabular data when Reacting Channel Area Option is set to Tabular .
Note If you are using additional re-entry zones, ensure that your tabular data cover for the total length of all channels.

This value is used to calculate the channel diameter

D_{C}

which is used to determine the convective heat transfer coefficient of the reacting channel,

h_{f}

in Eqn. (3813).

Inlet Mass Fractions

Allows you to specify the initial mass fraction profile of the components entering the reacting channel.

Inlet Pressure

Allows you to specify the pressure at the reacting channel inlet.

Inlet Temperature

Allows you to specify the reacting channel bulk temperature,

T

Inlet Velocity

Allows you to specify the velocity of the components entering the reacting channel inlet.

Packed Bed Heat Transfer Factor

Available when the reacting channel correlation type is set to Packed Bed. Allows you to specify the heat transfer factor,

f_{h t g}

, which is used to calculate the heat transfer correlation for the packed bed reacting channel in Eqn. (3817) and Eqn. (3819).

Packed Bed Particle Diameter

Available when the reacting channel correlation type is set to Packed Bed. Allows you to specify the equivalent packed bed particle diameter,

D_{p}

, which is used to calculate the heat transfer correlation for the packed bed reacting channel in Eqn. (3817) and Eqn. (3819).

Packed Bed Porosity

Available when the reacting channel correlation type is set to Packed Bed. Allows you to specify the porosity,

χ

, of the material within the packed bed reacting channel.

Pipe Friction Factor

The pipe friction factor,

f

, is available to specify as:

a constant value when Reacting Channel Pipe Friction Factor is set to Constant.
tabular data when Reacting Channel Pipe Friction Factor is set to Tabular.

This value is used to determine the Nusselt number for cases with turbulent flow, in Eqn. (3815), which is used to calculate the convective heat transfer coefficient, $h_{f}$ , in Eqn. (3813). It is also used to calculate pressure drop in Eqn. (3825).

Pipe Length

Allows you to specify the length of one geometrical channel in the reacting channel zone.

Re-Entry Boundaries

Available when the Reacting Channel Inlet Type condition for the reacting channel zone has the Inlet Type set to Re-Entry.

Provides a list of re-entry boundaries, that is, a list of boundaries which will receive incoming flow from an outlet boundary. You specify an Outlet Boundary for each re-entry boundary.

Make sure that the reacting channels are oriented correctly using the Orientation property of the Wall Orientation value node.

Solver Settings

Allows you to set the reacting channel solver settings for the zone.

ODE Solver Absolute Tolerance
ODE Solver Relative Tolerance

Under-Relaxation Factor

Allows you to set an under-relaxation factor,

a

, which governs the extent to which the old solution is supplanted by the newly computed solution.

Wall Discretization

Simcenter STAR-CCM+ receives a gradient of different temperature or heat flux values at intervals of this distance along the length of the reacting channel in the specified Wall Orientation.

Wall Orientation

Allows you to set the direction of flow in the reacting channels—which is important when simulating re-entry from one zone of reacting channels to another.

Conditions

Reacting Channel Species

PFR Species (read only): Allows you to see all species that are involved in this mechanism in the reacting channel—reactants and products.

Values

Coupling Strategy

Couple After Step: Specifies the time-step after which data is transferred from the Plug Flow Reactor (PFR) to Simcenter STAR-CCM+. Delaying the data transfer until a specified time step allows the solver to reach a level of stability while receiving data from the PFR, before sending data back to the PFR.
Coupling Frequency: Specifies the interval of time steps that occur between each transfer of data from the PFR to Simcenter STAR-CCM+.

Chemistry Definition


Node	Description / Properties
Chemistry Definition	Provides the right-click options to Import Chemistry Definition (Chemkin Format) or Delete Chemistry Definition. Properties: Material Database Path and Number of Species (both read-only).
Reacting System Properties
Species Reaction Sources	Properties: Method—Internal or User-Defined
Internal	Simcenter STAR-CCM+ defines the reactions from an internal set of standard Chemkin format reactions.
User-Defined	Allows you to define the reactions with user coding—useful for non-standard reaction types. Properties: User Function—when user coding is set up, the wdot option (the name of the function in the user code) becomes available. For an example of user coding for reacting channels, see the tutorial: Reacting Channels: Steam Methane Reforming.
User-Defined Species Sources Specification	Properties: Method—Calculate Species Sources or Modify Internal Species Sources
Calculate Species Sources	Properties: Internal Reaction Energy Source—when activated, calculates the reaction energy source internally for a constant pressure reactor based on user-calculated species reaction sources.
Modify Internal Species Sources	Existing internal species sources are modified.
Reactions	Provides the right-click option to create a New Reaction. Upon importing a chemistry definition / defining user coding, this node becomes populated with the appropriate reactions.

Reports

Reacting Channel Outlet Quantity

Units: Units for the quantity that is selected.
Reacting Channels: The report runs on the outlets of the reacting channels that are selected.
Quantity: The quantity that is reported at the outlet—such as temperature, velocity, heat flux, or a particular species.

Reference Values

Minimum Allowable Temperature

The smallest temperature value that is permitted anywhere in the continuum.

The Energy models (Coupled Energy, Coupled Solid Energy, Segregated Solid Energy, Segregated Fluid Enthalpy, Segregated Fluid Temperature) limit temperature corrections such that the corrected value does not go below this minimum. If this occurs, a message is printed to the Output window.

Maximum Allowable Temperature

The largest temperature value that is permitted anywhere in the continuum.

The Energy models (Coupled Energy, Coupled Solid Energy, Segregated Solid Energy, Segregated Fluid Enthalpy, Segregated Fluid Temperature) limit temperature corrections such that the corrected value does not exceed this maximum. If this occurs, a message is printed to the Output window.

Boundary Settings

Domain Boundary

External Code Coupling Specification: Allows you to assign the boundary to a co-simulation zone for coupling. During the co-simulation, the Simcenter STAR-CCM+ boundary exchanges data with the corresponding coupled surface in the partner simulation, according to the co-simulation zone specifications.