Clean Room: Corona Virus Patient Breathing

Description

This project simulates the steady-state breathing of a coronavirus patient inside a clean room using ANSYS Fluent.

Hospital rooms require dedicated air conditioning systems capable of continuously supplying fresh air to dilute and remove contaminated air surrounding the patient, while also maintaining proper cooling and heating. In this simulation, a bedridden patient inside a hospital room is modeled as the source of coronavirus transmission, with the patient's mouth explicitly defined as the point of respiratory viral release.

The patient's body surface is set to a temperature of 308 K, reflecting a common symptom of the illness. Fresh air supplied through the room's air purification system works to remove contaminated air and virus particles while simultaneously cooling the patient's body surface to maintain thermal comfort. To achieve this, several ceiling-mounted panels introduce fresh air at 294 K, with corresponding outlet panels positioned along the lower section of the side walls.

The 3D geometry was created in Design Modeler and meshed using ANSYS Meshing, resulting in an unstructured mesh of 5,666,870 cells.

Methodology

This simulation employs the Discrete Phase Model (DPM) to represent the patient's respiration and the resulting release of coronavirus particles. When studying the behavior of discrete particles suspended within a continuous fluid medium, the solution approach shifts from Eulerian to Lagrangian — tracking individual particle trajectories rather than treating them as part of the continuous flow field.

Since a coughing or breathing patient releases coronavirus particles as discrete entities into the surrounding air, this Lagrangian, particle-tracking approach is required. The DPM model is therefore used to define an injection representing virus particles released from the patient's mouth. These particles are modeled as inert, with a surface-type injection. Particle boundary conditions are set to escape when crossing domain boundaries, and to trap or reflect upon contact with wall surfaces.

Conclusion

The simulation results yield velocity, temperature, and pressure contours, along with airflow pathlines for the ventilation system. These results show that fresh air entering through the ceiling panels circulates throughout the room before exiting through the outlet panels.

Using the DPM approach, the released virus particles are tracked and shown to be carried by the ventilation airflow, ultimately directed toward the outlet panels and removed from the room.

Thermal comfort is also evaluated using two key parameters: PMV (Predicted Mean Vote) and PPD (Predicted Percentage of Dissatisfied). PMV, derived from human thermal-response data across various experimental conditions, depends on variables such as air temperature, humidity, air velocity, and occupant activity level, and ranges from -3 to +3. PPD is calculated as an exponential function of PMV and reflects the expected percentage of occupants dissatisfied with the thermal environment. The results indicate that both PMV and PPD values fall within an acceptable range, confirming suitable thermal comfort conditions within the simulated room.