Hospital Operating Rooms – HVAC Configuration Matters!

This is a follow-up to the previous post on airflow patterns in hospital operating room (OR). Previous Computational Fluid Dynamics (CFD) study of a legacy HVAC design of a hospital OR indicated that the supply airflow rates or air change rates (ach) have a little impact on reducing the particulate entrainment from non-sterile zone into the sterile zone. We evaluated several modifications in the legacy HVAC configuration to test whether such modifications can alter the flow path of these contaminants and mitigate the issue of particulate entrainment. One such modification involved changing the locations of exhaust grills. Unlike the legacy design with low wall exhaust, when the exhaust grills are placed in the ceiling with a small barrier around the ceiling supply diffusers, the entrainment of particulates from the non-sterile zone into the sterile zone reduced significantly. Further it helped in reducing the thermal gradients across the sterile zone by mixing the cold exiting air from the sterile zone with the warm air in the non-sterile zone, This not only creates thermally comfortable environment for the occupants but also reduces the air entrainment into the sterile zone and acceleration of the discharge air jet from the supply diffusers. This analysis indicates that strategic modifications can improve the performance of the operating room HVAC system even at low air changes rates. It can alter airflow patterns and resulting flow path of airborne particulates which can further help in reducing the entrainment into the sterile zone. According to the previous study such improvements were not possible by simply increasing the supply airflow rates or air change rates. In order to obtain the desired performance of the operating room HVAC system, proper optimization of supply and exhaust air locations is as important as the supply airflow rate.
Numerical computations for this study were performed using ANSYS/Fluent CFD software.