CONFIGURATION OF VENTHOLES SUPPORTING UNIDIRECTIONAL DOWNFLOW AS VENTILATION SYSTEM DESIGN AND AIR QUALITY OPTIMATION STRATEGIES IN NEGATIVE PRESSURED AIRBORNE INFECTION ISOLATION ROOM (AIIR)

• Main Author: Lotus Amala, Nabila
• Format: Theses
• Language: Indonesia
• Subjects: Teknik (Rekayasa, enjinering dan kegiatan berkaitan)
• Online Access: https://digilib.itb.ac.id/gdl/view/79891
• Institution: Institut Teknologi Bandung

The transmission risk of nosocomial infections through airborne particles depends on the air flow direction and pattern in the room, which affect the dispersion process of particles in the air. Therefore, it is necessary to attain an optimum ventilation system that can produce flow pattern supporting the contaminant particles dispersion, especially in the Airborne Infection Isolation Room (AIIR). AIIR uses a negative pressure system, where the indoor pressure is lower than the outdoor pressure. Ideal AIIR ventilation system can produce unidirectional downflow (UDF) air with characteristics include parallel, uniform, and regular streamlines and also flows from the cleaner space to the more contaminated space. In this study, performance analysis was carried out on alternative configurations of ventholes which were applied to the ventilation system of the negative pressured patient ward AIIR model. The purpose of this research is to determine the optimum ventholes configuration which the result airflow is closest to the ideal UDF flow pattern. The geometry model was built based on the requirements of Indonesian Ministry of Health and ASHRAE with a volume of 48 m3 and an exchange rate of 12 ACH (576 CMH). Airflow and particle tracking simulations were carried out to represent the airflow pattern and the contaminant particles dispersion patterns. Airflow simulation was done by using Reynolds-Averaged Navier Stokes (RANS) equation and applying k-? turbulent flow model. Airflow simulation results included streamlines, vectors and contours of air velocity at steady conditions and also standard deviations of velocity in the plane near the contaminant source. Particle tracking simulation used Newtonian particle movement system and was influenced by the drag force of the airflow. Contaminant particles were spherical droplet nucleus with a diameter of 5 ?m produced by patient's mouth and nose. The results of the particle tracking simulation included sequences of images that represented the changes of each contaminant particle position starting from the moment of particles released by the source until they are dispersed or they had no longer changing in position (dissipated). The dispersion pattern and profile can be used as a measure of air quality through dispersion probability and dispersion time. In terms of flow patterns, irregularities were found in all configurations, especially around patients and health facilities. In other words, there was no configuration that produced ideal UDF flow. However, the majority of streamlines are parallel and well behaved so that all configurations produce semi-unidirectional flow except configurations with significant flow separation as the consequence of exhaust grilles addition in the ceiling. Flow irregularities could increase the risk of infection to health care workers and dissipation of particles. Configurations with exhaust grills above the patient had faster maximum dispersion time, which is less than 400 seconds, but the upward dispersion path might improve the risk of infection for health workers. At the same time, configurations with the exhaust grills were positioned on the wall produced better dispersion pattern but the required dispersion time was longer. Based on qualitative and quantitative analysis from generated airflow, the optimum flow pattern for AIIR was generated by configuration that had dual-horizontal mounted wall exhaust grilles installation in the left and right of patient’s head with an average standard deviation of 34×10-3 m/s in the plane behind the patient's head. As for the dispersion pattern and dispersion profile of contaminant particles, the best configuration is configuration that had single-horizontal mounted wall exhaust grilles installation with dispersion probability close to 100% within 1000 seconds. Both optimum configurations had horizontal installation of exhaust grills at the bottom of the wall near the patient's head and a supply air diffuser in the center of the room ceiling.