Ventilation plays an important role in reducing the concentration of infectious aerosols and the risk of infection transmission in indoor environments. In this thesis,
natural and mechanical ventilation were compared using two geometrically identical
models of a dining area in a small company. Computational fluid dynamics (CFD)
was used to determine the three-dimensional steady-state velocity field and the mean
age of air, which served as an indicator of the air renewal rate. The obtained velocity field was subsequently used as input to a three-dimensional advection–diffusion
model to calculate the spatial distribution of infection quanta concentration. Based
on the local concentrations, the Wells–Riley model was used to estimate the probability of infection throughout the room and in selected areas near the sofa, table,
and counter.
The analysis of the mean age of air showed that mechanical ventilation provided
faster air renewal, although the renewal was not uniform throughout the room. In
the scenario considered, mechanical ventilation reduced the mean concentration of
infection quanta by 61.4 % and the mean probability of infection from 8.01 % to
3.17 %. The probability of infection decreased in all analysed areas, with the largest
reduction near the sofa and the smallest near the counter. The maximum concentration decreased by only 5.9 %, indicating that local areas of increased exposure
may remain even with more effective ventilation. The results confirm that, when
assessing the effects of ventilation, the mean age of air and the spatial distributions
of airflow and infection quanta concentration should be considered alongside average
values. The calculated probabilities provide a comparative assessment of the two
scenarios rather than an accurate prediction of the actual number of infections.
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