Effect of Plasma on Water Evaporation (電漿對液滴蒸發之研究)
In contrast to droplet evaporation with a heat source, corona discharges may accelerate evaporation without heating up the droplet. The present study is to investigate the evaporation behaviors of water droplet under corona discharge. The corona discharge is produced with a pin-to-plate electrode arrangement and a high DC power supply. Of particular interests are the influence of voltage polarity, electrode gap and voltage amplitude on droplet evaporation. Results show that the evaporation rate of water droplet is enhanced with increased voltage and shorter electrode gap. A negative voltage has a stronger effect on accelerating droplet evaporation than a positive voltage, due to the larger overvoltage and the more diffusive ionic wind. Compared to natural evaporation, the evaporation rate under corona discharge can be enhanced up to three times. Corona discharge is also found to be more effective than a DC electric field on evaporation enhancement. The enhanced evaporation of water droplet under corona discharge is mainly associated with the Marangoni effect and the induced ionic wind.