Mechanism of Microwave Heating through Molecular Orbital Method and Bubble Size Profiles

In this study, mechanism of microwave heating on water was investigated through a combination of the experimental and simulation works on bubble formation. Fine bubbles were firstly observed and confirmed at the temperature below the boiling temperature of water using a reactor equipped with DLS system. It was hypothesized that thermal non-equilibrium condition such as a hot spot was formed under microwave irradiation. Secondly, the initial stage potential of bubble nucleation (clathrate), which consists of water molecules, was calculated through a molecular orbital method. From the experimental and simulation results, it was found that high energy was generated by the bubble collapse, reconstruction of water molecule clathrate, and repetition of clathrate formation and collapsing cause higher heating efficiency of microwave. Thus, it can be deduced that microwave heating is greatly influenced by clathrate formation and the collapse.