Performance of upper-room ultraviolet germicidal irradiation (UVGI) system in learning environments: Effects of ventilation rate, UV fluence rate, and UV radiating volume

Previous studies show that upper-room ultraviolet germicidal irradiation (UVGI) systems can help contain infectious airborne viruses indoors. However, there has been a lack of research on the performance of an upper-room UVGI system in learning environments such as a school classroom. Since classrooms are more vulnerable to airborne transmission of diseases due to high occupancy for long hours, airborne infection characteristics are different from other occupied indoor environments (e.g., offices and residences). The objective of this study is to investigate UVGI system performance in a classroom considering detailed effects of ventilation rate, UV fluence rate, and UV radiating volume. Two analytical models, a one-zone and a two-zone material balance model, along with computational fluid dynamics (CFD) simulations, were employed to analyze viral aerosol concentrations under a representative range of classroom operating conditions. The CFD results show that increasing ventilation rate from 1.1 h–1 to 5 h–1 yields about 85% of airborne disinfection while doubling UV radiating volume results in a 60% disinfection. However, increasing UV fluence rate from 25 μW∙cm–2 to 50 μW∙cm–2 yields a moderate additional disinfection of 18%. Overall, the study results reveal that operating a UVGI system in an occupied classroom can markedly disinfect airborne viruses up to 96%, which is as effective as increasing ventilation rate more than five times. Furthermore, the results suggest that the one-zone and two-zone analytical models used in several previous studies could result in notably meaningful errors in analyzing viral aerosol concentrations, especially in occupied rooms with a highly non-uniform airflow distribution.

Identification of Direct-Use Geothermal Energy for Extracting Cajuput Oils Used to Reduce Respiratory Disorder Due to COVID-19

The COVID-19 disease causes severe symptoms like fever, cough, and respiratory disorder like streptococcus pneumonia. Essential oil in cajuput is oil is believed to have effect to reduce respiratory disorder due to COVID-19. While the cajuput oil is not proven to prevent or to heal COVID-19 patients, the treatments using cajuput oil are proven helpful to ease the symptoms. Indonesia as a tropical country has large-scale cultivation of cajuput plants, for example in 2017, Sumedang and Majalengka areas produced up to 4 tons raw material or 10 kg in a day. In producing cajuput oil, there are some steps required for oil extraction and distillation including modified steam distillation method used in this study. This method of essential oil extraction process may use a large amount of heat to produce steam. Geothermal residual heat in the form of brine can be an alternative used to extract eucalyptus oil on small scale. This study shows the material balance analysis for the cajuput oil production with 10 kg cajuput leaves per day from Sumedang and Majalengka areas using Wayang Windu geothermal power plant brine at 180.7°C with 0.05 kg/s mass flow rate. Wayang Windu geothermal power plant itself was chosen because the distance is not too far from cajuput source, which is around 99.7 km. In this study the cajuput oil extraction produces around 57.918 × 10−3 kg of cajuput oil for daily production time 100 min/day.