Abstract
Cold atmospheric plasma is a potential tool for medical purposes, e.g. disinfection/sterilization. In order for it to be effective and functional, it is crucial to understand the transport mechanism of chemically reactive species in air as well as in liquid. An atmospheric plasma discharge was produced between a platinum pin electrode and the surface of water. The thermal flow field of a cold atmospheric plasma as well as its chemical components was measured. A gas flow with a velocity of around 15 m s−1 to the water's surface was shown to be induced by the discharge. This air flow induced a circulating flow in the water from the discharge point at the water's surface because of friction. It was also demonstrated that the chemical components generated in air dissolved in water and the properties of the water changed. The reactive species were believed to be distributed mainly by convective transport in water, because the variation in the pH profile indicated by a methyl red solution resembled the induced flow pattern.
Highlights
Of the water’s surface was as high as the glass cell
By applying a high voltage of 7.5 kV0p with a square wave at 5 kHz with respect to the ground, a plasma discharge was produced between the tip of the platinum electrode and the water’s surface
At t = 5 s, the yellow region has a conical shape and this shape is very similar to the flow pattern measured by the particle image velocimetry (PIV) method shown in figure 5
Summary
Of the water’s surface was as high as the glass cell. During our experiment, the evaporation of water was negligible. By applying a high voltage of 7.5 kV0p with a square wave (duty ratio 50%) at 5 kHz with respect to the ground (using a high-voltage amplifier; TREC, model PD05034), a plasma discharge was produced between the tip of the platinum electrode and the water’s surface (see the inset of figure 1). Microparticles of polymethylmethacrylate, 5 μm in diameter, were used for particle image velocimetry (PIV) for observing the flow pattern in water.
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