UVGI Air Sterilizer in Air-conditioners

Abstract

The purpose of this paper was to present the design of an air sterilizer to improve the indoor air quality in classrooms of educational institutions. Presently, there is a risk of spreading Coronavirus-2 (SARS-CoV-2) which is an emerging disease that continuously mutates affecting respiratory system of students. The spread of airborne transmission has Increased the number of infected people. Crowded classrooms in educational institutions are one of risky places in spreading rapid epidemic. Therefore, improving the quality of contaminated air is essential to make it recirculate. Ultraviolet Germicidal Irradiation (UVGI) or the use of Ultraviolet-C can eliminate viruses and bacteria that spread in the air. Therefore, the researcher has an idea to apply the airborne virus elimination method with the operation of air conditioning system to solve the problem to improve indoor air quality in educational institutions. The researcher used 3 sets of UV-C 6W lamps with 30 cm long. To determine the wavelength of each lamp using UV Light meter, it was found that the wavelength of each lamp was 0.381 mW/cm2 (3.81 W/m2) with UV dose of 3.81 J/m2. They can eliminate viruses by installing in a device designed with an internal flow length of 1.5 m at an air flow rate of 3 m/s. According to a relevant study, Hao Luo et al. (2021), it was found that in a UV intensity range of 3.81 J/m2, viruses can be eliminated at 80% with the wind speed of 3 m/s and the vent volume of 0.35 m x 0.35 m x1 m. It can be concluded that an increase of the air flow rate and the lamp number resulted in the efficiency of virus elimination. The UVGI was applied in inventing a prototype of an air sterilizer in household air conditioners by using 2 sets of 8W UVC. The prototype was low cost with high efficiency in improving indoor air quality. The results of the experiments showed that the developed air sterilizer can reduce the mold growth and relative humidity by 50%. Based on the results of this study, the knowledge gained from the study can be applied in the design and construction of an air sterilizer used in educational institutions.