Simulation of micromachined chemical reactors for heterogeneous partial oxidation reactions

We present Galerkin finite element simulations of two- and three-dimensional fluid flow, thermal fields, and chemical species concentrations in micromachined chemical reactors. Such microchemical systems have potential for increased safety and on-demand manufacturing compared with conventional macroscopic reactors. The simulation approach incorporates a general mesh generation procedure that enables different microchemical reactor designs to be explored. The nonlinear differential-algebraic equations resulting from the finite element discretization are solved by Newton's method augmented with a pseudo-arc-length continuation scheme for tracing ignition and extinction points. The predicted temperature profiles are in good agreement with experimental data from temperature sensors located along the heater unit of the microreactor. The results also mirror observed ignition–extinction behavior by demonstrating that at low flow rates ignition occurs downstream and the reaction front subsequently travels upstream due both to heat conduction and the presence of fresh reactants upstream. Upstream movement of reaction front diminishes at high flow rates because significant reactions occurring downstream cause the downstream temperature to climb. The good agreement between simulated and observed results encourage further use of reaction engineering analysis and design tools in evaluation, scale-up, and application of microchemical systems.

[1]  Lanny D. Schmidt,et al.  Kinetics of NH3 oxidation on Pt, Rh, and Pd☆ , 1975 .

[2]  Michael P. Harold,et al.  Micromachined reactors for catalytic partial oxidation reactions , 1997 .

[3]  Norbert Schwesinger,et al.  A modular microfluid system with an integrated micromixer , 1996 .

[4]  K. R. Westerterp,et al.  Safe design of cooled tubular reactors for exothermic, multiple reactions; parallel reactions—I: Development of criteria , 1984 .

[5]  Robert J. Kee,et al.  A FORTRAN COMPUTER CODE PACKAGE FOR THE EVALUATION OF GAS-PHASE, MULTICOMPONENT TRANSPORT PROPERTIES , 1986 .

[6]  O. C. Zienkiewicz,et al.  The Finite Element Method: Basic Formulation and Linear Problems , 1987 .

[7]  Klavs F. Jensen,et al.  The Effect of Multilayer Patterns on Temperature Uniformity during Rapid Thermal Processing , 1996 .

[8]  O. Levenspiel.  Chemical Reaction Engineering , 1972 .

[9]  S. D. Senturia.  CAD For Microelectromechanical Systems , 1995, Proceedings of the International Solid-State Sensors and Actuators Conference - TRANSDUCERS '95.

[10]  R. Glowinski,et al.  Computing Methods in Applied Sciences and Engineering , 1974 .

[11]  I. Babuska,et al.  Finite Element Analysis , 2021 .

[12]  J. Heimerl,et al.  A comparison of transport algorithms for premixed, laminar steady state flames , 1980 .

[13]  Robert L. Lee,et al.  The cause and cure (!) of the spurious pressures generated by certain fem solutions of the incompressible Navier‐Stokes equations: Part 2 , 1981 .

[14]  A. Berg,et al.  Micro Total Analysis Systems , 1995 .

[15]  Frank P. Incropera,et al.  Fundamentals of Heat and Mass Transfer , 1981 .

[16]  S. Saxena,et al.  Thermal conductivity of binary, ternary and quaternary mixtures of rare gases , 1967 .

[17]  Eurosensors.  Transducers '95 = Eurosensors IX : The 8th International Conference on Solid-State Sensors and Actuators, and Eurosensors IX. June 25-29, 1995, Stockholm, Sweden : digest of technical papers , 1995 .

[18]  D. R. Stull.  JANAF thermochemical tables , 1966 .

[19]  M. K. Drost,et al.  Developing new miniature energy systems , 1994 .

[20]  P. Hood,et al.  Frontal solution program for unsymmetric matrices , 1976 .

[21]  D. Braess.  Finite Elements: Theory, Fast Solvers, and Applications in Solid Mechanics , 1995 .

[22]  R. Reid,et al.  The Properties of Gases and Liquids , 1977 .

[23]  T. Hughes,et al.  Streamline upwind/Petrov-Galerkin formulations for convection dominated flows with particular emphasis on the incompressible Navier-Stokes equations , 1990 .

[24]  W. Ehrfeld,et al.  Microreactor with Integrated Static Mixer and Analysis System , 1995 .

[25]  Klavs F. Jensen,et al.  A Systematic Approach to Simulating Rapid Thermal Processing Systems , 1996 .

[26]  Wouter Olthuis,et al.  Modular concept for miniature chemical systems , 1995 .

[27]  Jan J. Lerou,et al.  Chemical reaction engineering : A multiscale approach to a multiobjective task , 1996 .

[28]  Klaus Schubert,et al.  Monolithic Microreactors Possessing Regular Mesopore Systems for the Succesful Performance of Heterogeneously Catalysed Reactions , 1998 .

[29]  W. Deen.  Analysis Of Transport Phenomena , 1998 .

[30]  K. Jensen,et al.  Investigation of high-temperature degradation of platinum thin films with an in situ resistance measurement apparatus , 1998 .