Influences Of Ground Thermal Conditions On The Ventilation Performances Inside Courtyards

With the acceleration of urbanization and the increasing of the population density in urbanareas, courtyard type buildings are widely used in modern urban architectural layout. Courtyardbuildings not only have advantages in improving lighting conditions and,provarcies in buildingsbut also can make full use of natural ventilation to create good microclimates of the buildingsand reduce buildings’ energy consumption.Although the courtyard can provide good microenvironments in such buildings, there exists apotential risk-internal contaminations are not easy to remove. At the same time, the interiorspace of the courtyard also is the transition of indoor and outdoor space, it is directly connectedwith the outside world, the external and internal pollutants will through the interior space into theinterior courtyard building, so the air quality of the interior space of the courtyard will have adirect impact on the indoor environment and human health.Despite the courtyard buildings are more and more polular in the current days, studies on thepollution Performances and contaminant removal mechanisms in courtyards are still lack，especially when pollution sources accompanied with heat sources in the courtyard. In this thesis,flow pattern, pressure distribution and pollutant distribution are simulated by employing thecomputational fluid dynamic (CFD) methods, and the impacts of the courtyard structure on theventilation Performances under different ground thermal conditions and wind directions arediscussed and.The numerical results indicate that the air flow field of the courtyards’ internal space willchange with the ground thermal intens ity-the greater ground thermal intensity, the greater airvelocity inside the courtyard. The interior air of the courtyard mainly enters from the topopenings and does not change with the variations of the intensity and wind directions. At thesame time, the ground thermal intens ity have a significant impact on the courtyards’ ventilation,the higher the ground thermal intensity, the higher the air change rate, and this effect exists in all wind directions.Under the most of wind directions, the absolute value of static differential pressure increaseswith the increasing of the thermal intensity of the ground. When the direction of room ventilationis from outside to inside courtyard, room ventilation is obviously enhanced by the thermalintensity of the ground. And thermal intensity can reduce or prevent the pollution source growingwith the heat source to contaminating the most of rooms in the courtyard.The ground thermal intens ity and wind directions have a direct impact on the pollutantdistribution inside the courtyards, but the influence of the ground thermal intensity is greater thanthe effect of the wind directions. And furthermore, with the increasing of the ground thermalintensity, the pollutants concentration inside courtyards decrease, and it is better for theimprovement of the internal air quality. When the ground is isothermal, the pollutantconcentrations in occupants breathing zone are greater than the whole space of the courtyards.However, this situation could be improved when the ground thermal intensity-the pollutantconcentrations of occupants breathing zone are similar to the whole zone of the courtyards. Atthe same time, the ground thermal intensity have a direct impact on pollutant dispersion ins idecourtyards, heat source intensity, the decreasing rates of the pollutant concentrations will increasewith the increase of ground thermal intensity. When the windward opening is large, theimprovement of air quality in the breathing zone by the ground thermal intensity is better thanthat in the entire courtyard space.