### Abstract

A general lumping analysis of a reaction system coupled with diffusion is presented. This analysis can be applied to any reaction system with n species for both steady-state and transient conditions. Here we consider lumping by means of an n̂ × n constant matrix M with rank n̂ (n̂ ≤ n). When the diffusivity is independent of position and concentration, represented by the vectors r and y, respectively, it is found that under steady-state conditions, a reaction system having a species concentration vector y(r) coupled with diffusion is exactly lumpable if and only if there exist nontrivial fixed J^{T}[y(r)]D^{-1}-invariant subspaces M [here J^{T}[y(r)] is the transpose of the Jacobian matrix for the chemical reaction rate vector f[y(r)] and D^{-1} is the inverse of the constant effective diffusivity matrix], no matter what value y(r) takes; under transient conditions, there exist simultaneously D- and J^{T}[y(r, t)]-invariant subspaces M. When D is a function of position or concentrations, M is simultaneously invariant to J^{T}(y) and D(r), D[y(r)] or D[y(r, t)]. The approach used to determine the constrained approximate lumping schemes for a nondiffusion system can also be used in a reaction-diffusion system, except that the constant basis matrices A_{k}'s of J^{T}(y) are replaced by B_{k} = A_{k}D^{-1} under steady-state conditions, or the extra matrix D is added under transient conditions. For n onconstant D, the basis constant matrices D_{i}'s of D(r), D[y(r)] or D[y(r, t)] are added.

Original language | English (US) |
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Pages (from-to) | 2041-2053 |

Number of pages | 13 |

Journal | Chemical Engineering Science |

Volume | 46 |

Issue number | 8 |

DOIs | |

State | Published - 1991 |

### All Science Journal Classification (ASJC) codes

- Chemistry(all)
- Chemical Engineering(all)
- Industrial and Manufacturing Engineering