• Bhaswati Choudhury,
• Judith Johnson
• Subrata Roy

ABSTRACT

Enhanced distribution of atmospheric surface dielectric barrier discharge (SDBD) generated ozone in air for effective decontamination is examined. This is achieved through experimental measurement and numerical prediction of the flow and ozone distribution produced by surface DBD plasma reactors kept in a closed chamber. This study provides an alternative technique for decontamination of assembly cleanroom facilities and spacecraft components. Conventional methods like dry heat microbial reduction and vapor phase hydrogen peroxide used in spacecraft related decontamination lead to thermal and chemical damage of sophisticated materials. Advantages associated with atmospheric DBD plasma decontamination like low temperatures, no organic-residuals and design flexibility make it a potential alternative to these methods. In this study, spore forming bacterial species, Bacillus subtilis, which is commonly used in planetary protection studies was used as the test organism. Significant reduction (~78%) of bacterial concentrations in the inoculated volume of air was observed using the comb shaped DBD plasma reactor. Increased reduction (~98%) was observed when the same reactor was used in conjunction with an external fan for better ozone distribution. Considering this, a recently developed DBD configuration called the fan SDBD reactor can be used instead of the external fan to obtain better ozone distribution leading to lower ozone requirements and energy consumption. For this purpose, ozone distribution in a chamber with the comb and fan SDBD reactor were compared experimentally. The fan SDBD reactor uniformly distributed ozone from the center towards the walls of the chamber with higher ozone concentrations at the center. In contrast, the comb SDBD reactor pushed the ozone towards one of the walls resulting in biased distribution with higher concentrations in one direction. These results suggest that the fan reactor is better suited for decontamination applications like sterilization of space craft components where a more uniform decontamination is preferred requiring less ozone concentrations. Preliminary simulation results of flow and ozone distribution by the comb and fan reactors up till 10 seconds of powering up are validated with experimental data. Such numerical simulations of ozone distribution resulting from different SDBD configurations can be used to develop and optimize reactor configurations for planetary protection decontamination applications.