Multidirectional Polarization Impacts on Microwave Heating Efficiency: A Molecular Dynamics Research of Microwave Heating of Common Solvents

Abstract

Energy efficiency has always been an inherent problem of microwave heating. In this work, the higher heating efficiency of the elliptically polarized microwave electric field is investigated via MD simulations, aiming to examine the multidirectional polarization effect during microwave heating. The MD results show that the heating efficiency growth rates of EtOH, AcOH, DMSO, H2O, and DMF are 3.17%, 3.92%, 4.14%, 5.00%, and 27.06% sequentially larger with the elliptically polarized microwave electric field (EF) than those with the linearly polarized microwave EF. Energy analyses indicate that the utilization rate of microwave energy would be increased of the elliptically polarized microwave EF with the same electric field intensities. The higher decay speed of the rotation autocorrelation function curves of elliptically polarized EF presents that the sample molecules do have a more frequent rotational motion to align with the varying polarization directions. Additionally, dielectric properties analysis gave the relation between the heating efficiency growth rate and the loss tangent of the samples. This microwave heating method is expected to be a new route to improve the microwave heating efficiency.

Microwave Hyperpolarization Effect─An Orthogonal Incoherent Microwave Field Heating Study

“…The nonequilibrium MD simulations were performed in a microcanonical (NVE) ensemble with an initial temperature and pressure of 300 K and 1 atm, respectively. Other details of MD simulations can be seen in the literature . In MD simulations, there are also two different heating modes that correspond to the experiment.…”

“…Other details of MD simulations can be seen in the literature. 43 In MD simulations, there are also two different heating modes that correspond to the experiment. The applied microwave electric fields of the two heating modes can be expressed as follows…”

Hierarchical core–shell Ni@C-NCNTs nanocomposites tailored for microwave-induced dry reforming of methane process

“…The microwave "non-thermal effect" could be understood as the microwave polarization effect on the spatial orientation and the high kinetic energy of reactive site collision, thus increasing the effective probability of molecules and reducing the chemical reaction activation energy. 69,70 This means that the DRM process in the microwave eld can be carried out with faster rate at a lower temperature. It could also be observed that the H 2 /CO ratio of MW-DRM process is higher than that of the conventional heating, which could be explained by the promotion of methane decomposition reaction under microwave irradiation due to the locally enhanced temperature caused by "hotspots" and plasma.…”