Reacting Channels

The Reacting Channel Coupling feature provides the ability to exchange data between a three-dimensional Simcenter STAR-CCM+ simulation and a one-dimensional Plug Flow Reactor (PFR) simulation which uses the CVODE solver. 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.

When simulating Reacting Channels, you simulate combustion in the three-dimensional background phase which surrounds the reacting channels. The Flamelet Generated Manifold model is often the most appropriate model for simulating combustion in a firebox surrounding the reacting channels. This functionality is useful for simulating chemical processes such as methane steam reforming and cracking.

When the Reacting Channel model is selected along with the Co-Simulation model, an External Links > Reacting Channel Co-Simulation node appears.

Several geometrical channels can represent one reacting channel zone—as long as all of the geometrical channels have identical geometries of the same orientation. For geometrical channels that differ in length, diameter, or orientation, define each different group of geometrical channels as a separate reacting channel zone. It is possible to model a reacting channel simulation in which a reacting flow exits channels in one zone and re-enters channels in another zone. The geometry of the reacting channels does not need to represent reacting channels that are physically connected by a U-bend, as long as the reacting channel boundaries are defined in Simcenter STAR-CCM+.

Simcenter STAR-CCM+ meshes and solves the volume of the outer flow. The reacting channels are solved using a Plug Flow Reactor (PFR) approximation. The reacting channels are not meshed and are considered 1D. However, the outer flow volume must account for the presence of the reacting channels in its geometry.

The coupling happens on the reacting channel wall boundary between the outer flow in Simcenter STAR-CCM+ and the reacting channel in the PFR. The temperature is exchanged from the outer flow to the reacting channel and heat flux is returned back from the reacting channel to the outer flow. Although reacting channels appear as 3D features in a geometry, they become 1D representations when defined as reacting channels in the Reacting Channel Coupling model.

Since the reacting channels are one-dimensional and have no mesh, data is exchanged between axial points, whose frequency you specify, along a vector through the centre of the reacting channel and the surface boundary of the outer flow, as represented by the diagram below:

Reactions that occur in a reacting channel can be endothermic (absorbing heat) or exothermic (releasing heat). At specified time intervals, Simcenter STAR-CCM+ sends the temperature along the geometrical channel wall to the Plug Flow Reactor (PFR). The PFR then solves for the reacting flow, determines the temperature within the reacting flow, and calculates the heat flux at each axial point in the reacting flow channel. The PFR then sends this data back to the outer flow in Simcenter STAR-CCM+. See Eqn. (3826).