Indoor environment of a classroom in a passive school building with displacement ventilation

Indoor air quality and thermal comfort of the passive school buildings should be particularly paid more attentions due to those new passive school buildings adopted highly airtight building envelopes. In this study indoor environment of a very densely occupied classroom with displacement ventilation has been investigated. In order to appropriately model the classroom, all the simulation parameters are based on a typical real classroom structure, its air tightness and infiltration rate were measured. CFD (Computational Fluid Dynamics) simulations were then performed for a typical summer day in Munich in the accordingly modelled classroom. Representative thermal comfort parameters e.g. vertical temperature difference between ankle and head, and percentage of dissatisfied etc. have been analyzed and evaluated.  The results obtained show that the displacement ventilation in the present work could provide generally favourable human thermal comfort and at the same time guarantee high indoor air quality indicated by the CO2 concentration in the occupant regions. Numerical results demonstrate that promotion of mechanical ventilation rate can simultaneously enhance the dilution of indoor air pollutants and the non-uniformity of indoor pollutant distributions.   Moreover, those results derived from the spatially and temporally resolved 3D distributions of the indoor air temperature and CO2 concentration, respectively, can help find the appropriate locations in the classroom for a single temperature and CO2 sensor inside the classroom to representatively measure the indoor air temperature and CO2 concentration in a long running term.