Towards miniature multi-bore coaxial reactors for microwave-assisted parallel liquid heating: Basis experimental research

This paper proposes the concept of miniature multi-bore coaxial reactors with potential applications in microwave-assisted combinatorial chemistry. The reactor consists of a shielded cylindrical dielectric core with multiple bores. Current-carrying wires contain several or only one bore, while others support the flowing liquids that are heated in parallel by the wire's electrical field. Initially, the design concept is confirmed through COMSOL electromagnetic numerical simulations of modes propagating in multi-bore coaxial waveguides. Experimental proofs are obtained by investigating the microwave heating of flowing ethanol, methanol, and reverse-osmosis water in a two-bore alumina eccentric coaxial waveguide, where the second channel contains an open-ended current-carrying wire. Joint analyses of temperature profiles, measured by an optical fiber sensor at three points of a PTFE liquid-filled tube installed inside a bore, and of input and reflected power curves measured by microwave meters, are performed. The results demonstrate adequate parallel heating of liquids using an open-ended wire heater, a configuration that can be extended to other multiple-bore coaxial reactors. It is expected that the proposed concept, confirmed by experiments and simulations, will find applications in multi-tube liquid heating and MW combinatorial chemistry.