The Study On Numerical Simulation Of Natural Ventilation In Green Building

Green building is an effective solution for over consumption of energy and resource used for city construction. Not only can the natural ventilation satisfy the room comfort requirement, but also save the costs of device, run and maintenance. The natural ventilation can construct green building environment that develops continuously as well.The paper studies on the temperature field and velocity field of the room that applies natural ventilation. The paper also analyses the micro environment around human body, like temperature unevenness, relative humidity, velocity and comfort level, and analyses the different influence degree of every factor on the same working condition.The numerical simulation of two types of natural ventilation: wind pressure and combined work of wind pressure and heat pressure, is done by using the computation hydromechanics software. In order to highlight the study value, the work bases on the climate characteristics in Tianjin area. Because of the visible effect of wind pressure in transitional seasons in Tianjin, the tilting solar chimney is installed on the house roof in order to enhance the effect of heat pressure. The simulation results show that the airflow rate with solar energy funnel is 1.6 times as much as that using wind pressure. The numerical simulation of the indoor airflow organization influenced by solar chimney is calculated for multiple working conditions, and the analysis of internal and external factors, like intensity of solar radiation, outdoor temperature, outdoor wind velocity, internal heat source and envelop structure etc., that affect the indoor heat environment, is also involved in the paper. Meanwhile, relative humidity, temperature efficiency, velocity, PMV and some other indexes are employed in order to evaluate the effect of indoor natural ventilation on different working conditions. The application scope of this type of natural ventilation is discussed at the point of view of energy conservation.The study indicates that outdoor temperature takes more effect on the indoor environment than the solar radiation does, when both heat pressure and wind pressure are considered. The numerical simulation results show that the combined work of heat pressure and wind pressure is suitable for the 20～25℃of outdoor temperature in Tianjin area. In Tianjin, the average intensity of solar radiation is the highest at time from 12:00 to 13:00 of a day in June. In this period of time, the airflow rate has the highest value. The variation of position and heating effect of the human body heat source, and the consideration of latent heat bring different influence degree to the air speed, temperature and relative humidity around the body. The rate of ventilation and the difference between indoor and outdoor temperature change with the variation of wind pressure. When the outdoor wind speed exceed 0.6m/s, the wind pressure can have great impact on the natural ventilation that effected by heat pressure. The material and thickness of the envelop structure take no effect on the indoor wall temperature in transitional seasons when using natural ventilation.