NUMERICAL ANALYSIS OF VENTILATION SYSTEM OF AN ISOLATION ROOM FOR A HOSPITAL

Abstract

Heating, ventilation and air conditioning (HVAC) of hospitals is a highly specialized field now .a days and, critical care units like Isolation rooms and Operation theaters deserve special attention. In view of the recent threats like AIDS, SARS and bio-terrorism (Anthrax), the importance of appropriate ventilation strategies for Isolation rooms in the hospitals has increased manifold. The infected or the infectious patients are supposed to be isolated from the ambient environment so as to save the life of the patient or to prevent the infection from spreading and to this end, the airflow pattern inside the isolation space proves detrimental. The present work contains the details of investigation of air diffusion, and comfort issues by CFD (computational fluid dynamics) modeling of an Isolation room for a hospital. Three types of cases have been chosen for ventilation of an Isolation room - a unidirectional ventilation system for an immuno-suppressed and an infectious patient each and a mixed ventilation system for an infectious patient. The patient's bed has been kept alternately near the supply sidewall and the exhaust sidewall for unidirectional airflow system and directly under the ceiling supply vent in the mixed ventilation system. The creating of required geometries, and meshing thereof, have been done using GAMBIT and the CFD solutions are obtained by using a software Fluent. The patient's body is simulated as a cylinder with approximate values for physical and thermal properties of a human body and treating it as a constant heat source. The modeling domain is air inside the room. The height of the inlet vent in case of unidirectional ventilation has been varied while keeping the exhaust height fixed at 0.75' above the floor. The transient and then, steady state simulations are carried out to obtain the spatial distribution of temperature and velocity. Thermal indices like Predicted Mean Vote (PMV) and Draught Rating (DR) have been custom-defined and a correlation is sought between the location of the IIT, Roorkee vi Thermal Engineering MIED Numerical Analysis of the Ventilation System of an Isolation Room for a Hospital supply and exhaust ducts and the thermal comfort experienced by the patient. The work also involves investigation into the motion and average residence time of a contaminant that could possibly accompany the supply air and the bacteria that can be released from an infectious patient's mouth by means of breathing, coughing or sneezing. The results reveal that whereas the height of inlet vent significantly affects the velocity and draught distributions and the residence times of bacteria and contaminant, it has no perceptible impact on the temperature and PMV profiles for the entire room so long as the velocities in the occupied zone remain low. It is observed that as the normalized height of the supply vent is decreased, more and more persons are likely to complain about draught - discomfort due to excessive cooling by the flow of air- in the occupied zone. Also, with lowering of the supply vent, the higher (near the ceiling) and lower (below the bed) zones of the room start showing stagnation. In such a situation, the location of bed of a particular patient inside the room becomes very critical and, it has been observed that an immuno-suppressed patient should be placed near the supply sidewall and an infectious patient should be placed near the exhaust sidewall of an isolation room. IIT,