Experimental Investigation of Operating Room Air Distribution in a Full-Scale Laboratory Chamber Using Particle Image Velocimetry and Flow Visualization

Room air distribution in hospital operating rooms (OR) is critical to the effective functioning of surgical procedures, but the air distribution patterns are governed by complex physics that are currently not well understood. Both qualitative and quantitative flow visualization techniques were used to evaluate the room air distribution in a full-scale chamber designed to simulate a hospital operating room. A laser sheet illumination technique was used to identify key features of the room air distribution, and particle image velocimetry (PIV) was used to measure the velocity field in a plane crossing the surgical site. Hospital operating rooms require the use of ASHRAE Group E diffusers in an array above the surgical table, providing downward, unidirectional, non-aspirating air flow across the sterile region of the room. The supply air jet is characterized by complex physics, including annular shape, impingement, buoyancy, a large jet to room aspect ratio, and recirculation. The large diameter of the jet relative to the room size makes the overall room air distribution highly sensitive to the parameters of the supply air. The air distribution pattern in the room was found to have relatively low velocity and turbulence near the supply air diffuser, but increasing velocity and turbulence in the shear region at the edge of the supply air jet. Flow visualization and PIV methods both demonstrated an angle of the shear layer inwards towards the center of the jet. This flow feature reduces the overall coverage area for the sterile air flow and may pose a risk to the protection of the surgical patient.