A Computationally Fast Method to Simulate Microwave-Heated Monoliths

Abstract

Microwave-assisted process intensification is a promising technique hindered by the unavailability of design rules for optimization and scale-up. High-throughput computational models allowing the exploration of a vast design space are imperative for the rapid development and deployment of intensified microwave reactors. Recently, structured reactors, especially monoliths, are emerging as a canonical multiphase reactor setup in the microwave-heating community. The vast separation of scales in these reactors leads to a large number of mesh elements, making the simulations time-consuming and challenging to converge. To this end, we employ volume and asymptotic averaging to represent monoliths, a multiphase system consisting of a fluid and a solid phase, as a continuum or effective medium. We rigorously verify the adequacy of the averaging techniques to predict the spatiotemporal distribution of the electric field, electromagnetic power dissipation, and temperature against fully resolved monolith simulations. The developed continuum model can replicate the three-dimensional transient behavior obtained from the multiphase simulations with an order of magnitude lower computational expense. Moreover, the continuum model allows easier mesh generation and convergence of numerical solution than the multiphase model. The developed multiscale framework can be used to simulate microwave-heated monoliths and other multiphase reactors, such as packed beds and open-cell foams.