Improvement of particle clean air delivery rate (CADR) of ion spray electrostatic air cleaner with zero ozone emission on diffusion charging in indoor space

A electrostatic precipitators (ESPs) type air cleaner applying ion spray charger was developed and evaluated. Unlike conventional ESPs type air cleaner, charger is located at the rear of collection stage. Ions are emitted to ambient space by fan of air cleaner, and airborne particles are charged by nearby ions based on diffusion charging mechanism. Hence, fan flow rate and collection area was directly affected to clean air delivery rate (CADR). Ion spray ESP showed particle CADR of 0.3 $\mu\mathrm{m}$ particle with 7.32 m3/min at the fan flow rate of 10.0 m3/min, and applied negative voltage of 5 kV to the ionizer and collection plate. In addition, generating ozone nearly zero in the closed chamber (30.4 m3), In addition, ozone concentration was about 0.58 ppb after 12 hours of continuous operation. Carbon brush fiber based charger without grounded plates is important key to achieve near non zero ozone emission. When ion spray ESP was operated at a particle CADR below 6 m3/min, it was satisfied the noise criteria. The particle CADR in actual environment increased 4.90 to 6.63 m3/min with elevating fan flow rate from 6.45 to 12.4 m3/min. In addition, it did not increase linearly but increased in logarithmic form and converging to a certain level as the fan flow rate increased because the structure of actual environment.