Numerical investigation of air conditioning system configurations for achieving desired negative pressure in isolation rooms

Abstract

This paper investigates a novel study about the influence of airflow simulation of an air conditioner (AC) inlet angle impacting negative pressure control in an airborne isolation indoor room (AIIR). The study focuses on four cassette Air Conditioner units set at different angles (0, 15, and 30 degrees) and their effect on air quality and airborne contamination removal for respiratory patients and healthcare workers by using computational fluid dynamics (CFD) simulations. Carbone dioxide is used as a tracer gas. The results showed that at a 0-degree angle, higher CO2 concentrations were observed compared to inclinations of 15 and 30 degrees at three minutes. Inclinations of 15 and 30 degrees promote better air circulation with medium and high velocity, better Contaminant Removal Effectiveness (CRE), and better local Air Quality Index (LAQI), facilitating efficient dilution and dispersion of CO2. In addition, these angles reflect the direction of airborne contamination to the side of the wall and keep them away from the healthcare workers, ensuring the medical staff's safety. In conclusion, The LAQI findings indicated an index value of 1.01 when measured at a 15-degree AC angle. In contrast, measurements taken at 0 and 30 degrees yielded values of 0.96 and 0.93, respectively, and the coefficient of restitution (CRE) exhibited values of approximately 100, 99.8, and 98 for AC angles of 15, 0, and 30 degrees, respectively, under low AC -velocity conditions.

Keywords

• iaq
• airborne infectious isolation room
• contaminant distribution
• cfd simulation
• tracer gas
• co2