Analysis of Airflow Distribution and Contaminant Flow Path in the Hospital Operating Room
ASHRAE Winter Conference, Las Vegas, NV, 2017
A probable factor in minimizing the infection due to airborne bacteria in the hospital operating room is to minimize the entrainment of air from the non-sterile zone into the sterile zone. A Computational Fluid Dynamics (CFD) model of a virtual hospital operating room is developed to analyze the impact of supply airflow rates or ACH on the airflow patterns, temperature distribution, and on the resulting flow path of airborne particulates. These analyses indicate the supply airflow rate, and hence, the discharge velocity of the unidirectional air jet, has a little impact on the overall airflow patterns and the thermal stratification in non-sterile zone occurs at all levels of supply airflow rates. Increasing the supply airflow rate and associated heat capacity of the supply air helps in reducing thermal gradients between the sterile and non-sterile zones which in turn may reduce the entrainment of the air from the non-sterile zone into the sterile zone. Increasing the supply airflow rate can also significantly reduce relative acceleration of the centerline velocity – an indication of the reduction in the entrainment. This study further indicates the supply airflow rate has a little impact on the overall flow path of airborne particulates. When these particulates are originated within a sterile zone they are generally swept away into the non-sterile zone where they can recirculate without significant re-entrainment before exiting the operating room. However, when these particulates originate from the non-sterile zone, irrespective of the supply airflow rate, they get entrained into the sterile zone. The flow of path of these particulates may need to be altered in order to avoid such entrainment. This can be achieved only by significantly altering the airflow patterns in the non-sterile zone. The legacy HVAC design for hospital operating rooms involving a ceiling array of laminar supply diffusers and low wall exhaust grills on the opposite walls may require further evaluation.