Aerosol dispersion and infection risk mitigation in a hybrid IJV-CRCP environment: the role of ventilation momentum and mask aerodynamics

Mitigating airborne viral transmission in enclosed public spaces, particularly acoustically sensitive conference rooms, remains a critical engineering challenge. While existing studies on radiant cooling predominantly focus on energy efficiency and thermal comfort, investigations into indoor air quality remain scarce. Specifically, the efficacy of combining Impinging Jet Ventilation (IJV) with radiant cooling to control aerosol transmission represents a critical knowledge gap. To address this, this study elucidates the aerosol dispersion dynamics within a hybrid air-conditioning environment coupling Capillary Radiant Ceiling Panels (CRCP) with IJV. Integrating CFD with the Wells-Riley risk assessment model, we quantify the interplay between ventilation momentum, mask leakage aerodynamics, and infection probability. Results identify a pivotal flow regime transition: a high-momentum IJV strategy (Modified Archimedes number Lm≈1.16) effectively suppresses thermal stratification ‘lock-up,’ significantly reducing aerosol residence time. Consequently, the spatial infection risk disparity between proximal and distal occupants is narrowed to a negligible 2.3%, demonstrating that high-momentum ventilation can effectively ‘democratize’ indoor safety. Furthermore, we uncover a critical aerodynamic trade-off in respiratory protection. While valveless N95 respirators achieve superior total containment efficiency (∼80%) compared to medical surgical masks (∼48%), their limited internal dead space induces high-velocity leakage jets (>15 m/s). Unlike the buoyant plumes typical of surgical masks, these jets entrain and project coarse droplets significantly further. These findings challenge the reliance on static concentration metrics, establishing that minimising exposure duration via optimised ventilation momentum is paramount for pandemic-resilient design.