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    Computational analysis of airborne particle behaviour in a single-bed intensive care unit with deflector implementation
    (ELSEVIER, RADARWEG 29, 1043 NX AMSTERDAM, NETHERLANDS, 2024) Çiçek, Oktay; Baytaş, Ahmet Cihat
    This study employs a one-way coupled Eulerian-Lagrangian model to investigate the behaviour of virus-laden particles emitted from three sources within a three-dimensional single-bed intensive care unit (ICU). The analysis encompasses the examination of airflow patterns and thermal fields alongside an assessment of the distribution, removal, and deposition mechanisms of particles. This investigation is conducted under a range of conditions, including variations in air inlet angle, the implementation of the deflector, adjustments in the position of both the patient bed and healthcare worker (HCW) and varying air inlet velocity. The temporal and spatial dynamics of particles released from the sources are analyzed in relationship to these mechanisms. The outcomes reveal that employing deflectors with suitable width and position diminishes the presence of suspended particles in the ICU and improves removal efficiency, thereby reducing the risk of infection. It is observed that an augmentation in the air inlet velocity results in a diminution of suspended particle concentrations in the ICU. Moreover, positioning the patient bed and HCW centrally or close to outlet vents enhances the particle removal efficiency. The particle concentration is analyzed for five different cases across each of the eight equally sized subsections of the intensive care unit, and the subsections with the lowest particle concentrations, indicating a reduced risk of transmission, are found. The findings can provide a beneficial perspective and guidance for strategic design in intensive care units focused on reducing the risk of infection transmission.
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    A numerical investigation of the particle behaviors and entropy generation in mixed convection inside a vented enclosure
    (ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER, 65 RUE CAMILLE DESMOULINS, CS50083, 92442 ISSY-LES-MOULINEAUX, FRANCE, 2023) Çiçek, Oktay; Baytaş, Ahmet Cihat
    The present study is to focus on the numerical investigation of the transportation, deposition and removal of solid particles in the range of 5 mu m to 0.01 mu m for mixed convection flow in the vented square cavity by utilizing the Eulerian-Lagrangian method with one-way coupling. The change in the deposition and removal mechanisms affected by the forces acting on the particles is addressed for mixed convection of ventilation airflow. In the analysis of entropy generation, the irreversibilities due to the presence of solid particles are studied with a new approach for both dominant natural and forced convection. The governing equations for fluid phase and the Lagrangian particle tracking are scrutinized by employing the finite volume method with SIMPLE algorithm and explicitly integrating the set of ordinary differential equations, respectively. The examination of the thermal and flow fields is carried out in the cases of various Reynolds numbers and Richardson numbers. The minimum and maximum values of the average Nusselt number are determined with related operating parameters. By using the results of thermal behaviors and flow structures obtained at steady-state condition, the particle velocity, temperature and location are presented for the combined natural and forced convection. By investigating the particles deposited on the walls and ones removed from the exit section for different Reynolds numbers and Richardson numbers, it is demonstrated that the sum rate of deposition and removal is low at 1 <= Ri <= 10 and high Reynolds number for 1 mu m and 0.1 mu m particles. For given Reynolds number, increasing the buoyancy effect results in substantial changes in the thermal field and flow pattern, therefore the particles remaining suspended show different behaviors when the effect of natural convection alters from weak to dominant. It is observed that the Brownian and thermophoretic forces play an important role in the small particle deposition and removal. As a result of entropy generation analysis, the minimum total entropy generation is determined at Ri = 5 for given Reynolds number except for Re = 50. Moreover, it is proposed to investigate the irreversibilities due to the heat transfer between the particles and the fluid surrounding them and the frictional total force acting on the suspended particles.