Development of a Test Methodology for Determining the Efficacy of One Atmosphere Uniform Glow Discharge Plasma Against Airborne Contaminants

A method of analysis is developed for an atmospheric plasma reactor in a ducted air stream with the intent of enabling parametric analysis for the multi-variable problem. Industrial uses for atmospheric plasma are numerous and in this case, a particular type of plasma known as “One Atmosphere Uniform Glow Discharge Plasma” (OAUGDP™) was studied for its chemistry generation abilities and its microorganism efficacy properties. The system of an OAUGDP reactor positioned in an air duct of fully-developed turbulent flow is constructed of nineteen pertinent variables and dimensional analysis is applied according to the Buckingham Pi method, yielding fourteen dimensionless variable groups. Important Pi groups are identified, namely those relating electrical power input to chemical generation and microorganism efficacy and experimental data is gathered and presented. Ozone is measured as a representative chemical and generation rates are presented in terms of airflow Reynolds number, geometry of the reactor electrodes and power input to the reactor.

A universal generation curve is developed for a parallel electrode reactor in which ozone generation rates can be determined from the known Reynolds number, electrode diameter to electrode gap ratio and plasma power to air flow power ratio. It is shown that ozone generation follows a bell shaped curve with increasing rates of production at a low ratio of plasma power to flow power, reaching a maximum and then decreasing to nearly zero at sufficiently high values of plasma power to flow power ratio. A principal area of development for OAUGDP and other atmospheric plasmas is for their use in destroying microorganisms, both on surfaces and in air streams. The ducted OAUGDP system was experimentally tested for efficacy against Bacillus atrophaeus endospores and results are presented in terms of the Reynolds number, the dimensionless plasma exposure time and the plasma power to airflow power ratio. Higher Reynolds numbers require higher treatment times for a given plasma power to flow power ratio.