A Study on the Naturally Ventilated Performances of the Envelop Openings

• Main Authors: PO-CHENG CHOU, 周伯丞
• Other Authors: CHE-MING CHIANG
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/87475388464880040722

博士 === 國立成功大學 === 建築學系 === 88 === The sustainability issues of recent studies are mainly focused on the energy preservation, environment protection, and economical development etc. One of the most beneficial senses is to utilize the natural driven forces to emphasize the air-exchange through the openings of the enclosure, and to reduce the dependence on utilizing the mechanical ventilation. This study, therefore, intends to develop the quantitative assess method as a tool during the design period to predict the naturally ventilated performances of rooms. Based on the literature review, numerical simulation was performed using CFD (Computational Fluid Dynamics) techniques. A full-scale bedroom Chamber was used in the experiments. Two types of windows were studied on the performances of different window positions and rotational angles. Our major findings were as below: 1. Close congruence with the experimental results shows the validity of numerical models. Those show CFD turbulence models in this study can act reasonably the role to predict the nature ventilation of buildings. 2. In the airflow of the forced convection, the standard k- model and the low-Reynolds number k- model are suitable, it, however, saves more calculated time using the standard k- model. In the airflow of the free convection, low-Reynolds number k- model performs more accurate, but a fine grid distribution near the wall boundary was necessary, and it took more calculated time. 3. In the seasons benefit the natural ventilation (spring & autumn), it is recommended utilizing cross-ventilation induced from the wind-pressure difference across the bedroom. For the bedroom-unit cases, wind-induced airflow was suitable for all of the window positions at the inlet wind-speed below 1 m/s. It was to avoid the window positions caused the mainstream through the head zone at the speed about 3 m/s. And, it was caused violently uncomfortable flow across the head zone as the air-draft effect for all of the window positions at the speed above 5 m/s. 4. In the seasons unfavorable for natural ventilation, especially in winter, it is used to close the door to keep warm in the sleeping nighttime. The single-sided ventilation, however, was harmful to provide convection. One of the solution is to utilize the central horizontal pivot window to introduce airflow into bedroom. For the bedroom-unit cases, when the window angle at 0-90°(cosθ>0), the airflow path induced from wind was against from stack, the ventilation efficiency at outdoor wind-speed UE = 0 m/s was more obvious than which at the slight wind-speed (UE = 0.3-0.5 m/s), the wind force, furthermore, become the major influence at wind-speed above 0.5 m/s. When the angle at 90-180°(cosθ<0), the airflow path induced from wind was overlapped from stack, the ventilation efficiency was greater accompanied the greater wind-speed.