The effect of air velocity and indoor ambient properties on the effective operating range of an air ionizer device

Abstract

Air ionizers are devices that purify the indoor air by artificially generating negative air ions (NAIs) which are proven to improve air quality and well-being of humans. Hence, more ionizers are being incorporated into heating, ventilation and air conditioning (HVAC) applications nowadays. . Every ionizer has its effective range of operation, which is the area inside a room that can potentially be covered by significant concentration of NAIs compared to the general concentration of ions naturally present in the room. This range may change depending on the indoor temperature, humidity and fan speed of the HVAC unit as preferred by the room occupants. Present research intends to design an experimental setup that could measure negative air ion (NAI) concentration at varying distances from an ionizer under different values of the aforementioned parameters. The experiment was conducted inside an indoor psychrometric test room to allow controlling of ambient temperature and humidity. Air velocity through the ionizer was varied from 1.5 m/s to 4.5 m/s, whereas the range of temperature and relative humidity were set from 25°C to 31°C and 60% to 80% respectively. To evaluate the ionizer’s operating range, NAI concentration was measured at every preset longitudinal (0 cm to 75 cm), lateral (-25 cm to 25 cm) and elevation (-15 cm to 15 cm) distance relative to the ionizer for 6 minutes using an ion counter named “Air Ion Counter Model AIC2”. The results reveal that the ionizer’s effective operating range increased with velocity, with the furthest range recorded at 4.5 m/s. Whereas a negative correlation was found between the ionizer’s effective operating range with temperature and humidity, with the furthest range recorded at 25°C and 60% respectively. The results also show that most ions were distributed in areas below and towards the right side from the ionizer’s perspective.