Air turbulence intensity influence on the thermal comfort evaluation for different ventilation strategies

Thermal comfort is a subjective term, closely related to the sensation of warm or cold for the occupants, defining the state of mind of humans that expresses satisfaction with the surrounding environment. Since we spend more than 90% of our time inside buildings or vehicles, achieving a good thermal quality of this enclosed environment is vital. An optimal thermal comfort prediction can lead to „bien-être”, efficiency in our work, unaltered health and even energy economy.
Among the newest and highly used approaches for thermal comfort studies are CFD methods, giving the possibility of extended parametric studies and in depth analysis of every thermo-fluidic parameter involved.
In this paper, several ventilation strategies were tested, in order to evaluate the thermal comfort of the occupants. We are comparing two mixing ventilation, and two displacement ventilation cases. This study is a part of larger experimental and numerical campaign intended to evaluate the influence of several flow parameters, such as the turbulence intensity at the inlet of the terminal air diffusion devices, on the local draft sensation and thermal discomfort of ventilation users. A numerical thermal manikin was placed in the centre of a test cell where different strategies of ventilation can be used. The results of CFD simulations were validated in a previous experimental campaign where a thermal manikin was used. While the PMV, and the PPD indexes seem to be less sensible to the value of the local turbulence intensity, the heat fluxes exchanged between the different body parts and their environment are highly varying between the studied cases. Local correlations between the turbulence intensity and convective heat flux of the body were found.