Propagation of humidified air plasma in a sandwich-type honeycomb plasma reactor and its dependence on the ambient temperature and reactor diameter

The dependence of the plasma discharge performance on the size of the honeycomb monolith in a sandwich-type honeycomb monolith plasma reactor operated under humidified air conditions was investigated. In addition, the effect of the feed gas temperature on the plasma discharge was also examined in the low-temperature range (25 °C–42 °C), which is similar to the typical temperature of the actual surrounding ambient air. The results showed that variation of the temperature significantly affects the discharge power, i.e., the discharge power decreases with increasing temperature. The results also indicated that, in the absence of the honeycomb monolith in the reactor, the plasma discharge did not occur inside the discharge zone created by two parallel perforated disks. However, when the honeycomb monolith was sandwiched between the two electrodes, the discharge developed between them because of the generated surface discharge spread through the honeycomb channels. Interestingly, a parallel relationship exists between monoliths with two different diameters in terms of their energy density and energy efficiency for O₃ generation. These results suggest that the use of a monolith with a small diameter, instead of the original large commercial monolith, is sufficient when conducting research on the honeycomb discharge, as it facilitates experimental design. (paper)