Virus dispersion in classrooms: CFD simulation comparing AC and chilled beam ventilation

Description

Virus transport analysis: CFD simulation of AC vs. chilled beam air distribution

Description

We simulated airflow, thermal comfort, and virus‐particle transport in a 10 m × 8 m classroom with eight occupants using ANSYS, comparing two HVAC concepts: a conventional AC layout and an active chilled-beam layout. The AC case used six 600 mm × 600 mm louvered inlets; the chilled-beam case used 12 circular inlets (Ø 100 mm) plus three chilled-water pipes at the ceiling. A virus source was located near the outlet, and particle trajectories were tracked to assess removal vs. mixing while also evaluating comfort via PMV/PPD.

Geometry and Mesh

The geometry of the room envelope, four desk rows, 24 monitors, eight seated humans, inlets/outlets, and ceiling beams, was built in SpaceClaim; both HVAC layouts share the same classroom furniture, with only the supply arrangement differing (louvers for AC vs. distributed nozzles/beams for chilled beams). The model was discretized in ANSYS Meshing with an unstructured grid of ~5,000,000 elements, refined around supply openings, occupants, desks, and near-wall regions to capture jets, recirculation, and thermal boundary layers.

Model and Solver Settings

A pressure-based, steady RANS solution with gravity (−9.81 m/s² in y) and the realizable k–ε turbulence model was used; the energy equation was active, and buoyancy used the Boussinesq approximation. Virus was modeled with a DPM surface injection (inert spheres, diameter 1 µm, 308 K, 0.05 m/s, total 5×10⁻⁷ kg/s), while AC inlets applied 0.4 m/s at 294 K and walls used appropriate no-slip and thermal conditions; the chilled-beam case matched the AC mass flow (≈1.0584 kg/s total) but supplied at a 30° angle to induce room-scale circulation, with beam pipes held at 290 K.

 Results

In the AC case, supply jets impinge and spread along the floor, sending colder air beneath desks. Near-wall regions are less well ventilated, leading to warmer zones and higher local PPD, despite acceptable average comfort. Meanwhile, virus-laden particles tend to travel directly toward the outlet with limited recirculation. In the chilled-beam case, angled supplies generate broader circulation, which improves temperature uniformity and PMV/PPD overall. However, the stronger mixing disperses particles throughout the room before extraction. Overall, AC favors faster removal of the virus source, while chilled beams favor thermal comfort at the cost of greater particle spread.