Particle Distributions In Rooms With Cooled Ceiling And Displacement Ventilation Combined Systems

The cooled ceiling-displacement ventilation (CC/DV) system is a new strategy of air conditioning combining the style of cooled ceiling and displacement ventilation, which could make use of the benefits of the two systems and complements for each other. The indoor air quality has important influences on human healthy, and the particulates are the main contaminant source indoors. Therefore, the studying on distribution and transportation of particles indoors could give some advises to improve the indoor air quality.According to the existed results, a computational fluid dynamic (CFD) model for predicting the aerosol particle dispersion in indoor spaces was validated with experimental data found in the literature. The validated model was used to study the indoor temperature field, flow field and particulate concentration field in a room with a CC/DV system and a displacement ventilation system, respectively. Comparing the simulation results for the two strategies in rooms, the impact of cooled ceiling system on indoor thermal comfort were analyzed and discussed. In order to explore the spatial distributions of aerosols indoors, two area particle sources were assumed at the height of Y=0.4m and 0.8m, respectively, and three locations of particle source, i.e. nearby the outlet, far away from the outlet and in the respiration zones, were considered for the study, respectively. The concentration distributions and the wall deposition loss were simulated and analyzed, and some comparisons between the CC/DV room and the displacement ventilation system were carried out. The influences of the cooled ceiling on the characteristics of particle dispersion and deposition rate for different sizes of particles were also estimated.In order to investigate the variations of indoor thermal comfort and indoor air quality in the CC/DV system room, two different heat resources were considered. The simulation result shows that different heat resources would result in different vertical gradient of indoor air temperature and airflow patterns. Because the aerosol dispersion is mainly determined by the flow field, the intensities of heat resources would cause the variation of particle distribution in the whole room. The characteristics of particle spatial distribution and wall deposition under different heat resources were analyzed by using the simulation results.