The proposed local dynamic similarity model of cross-ventilation predicted ventilation flow rates more accurately than the conventional orifice flow model assuming constant discharge coefficients when discharge coefficients actually decreased with change of wind direction. This model was used to develop a new method for evaluating the ventilation performance of window openings. The obstructive effect of model size on flow fields in a wind tunnel was avoided by installing the opening parallel to the wind tunnel floor.
In summer, it is possible to achieve a satisfactory comfort in residential buildings with purely passive means as thermal inertia, possibility of cross ventilation and solar protection of the external envelope. These parameters have to be taken into account at the earliest stages of building design.
Airflow through houses from onshore coastal breezes in warm humid tropical climates is the principal passive means of achieving indoor thermal comfort when air temperatures exceed 30°C and relative humidity exceeds 60%. Estimates of indoor natural ventilation cooling potential have been based on indoor wind speed coefficients determined from boundary layer wind tunnel tests combined with wind frequency, air temperature and relative humidity data.
Air change rates in a cross-ventilation model were measured from the decay curves of video image signals obtained by the step down method assuming perfect mixing of tracer mists inside the spaces. Wind tunnel test results led to the following conclusions. 1) Ray extinction due to lighting scattering did not affect the measurement accuracy of the air change rates in the two-dimensional model. 2) Tracer mists in a diameter between 0.25 μ m and 2.0 μ m produced the same measurement accuracy.
Natural ventilation can be a part of a strategy for a good indoor air quality. It can also be a way to realise night time ventilation during warm periods. In this latter case, the aim is to cool down the thermal mass of the building to obtain a better thermal comfort during daytime. Night time ventilation requires high ventilation rates and sufficient accessible thermal mass. The ventilation openings have to be well designed to avoid undesirable effects like rain, pollution and burglary.
In order to give some guidance for the optimization of shop entrances regarding comfort and energy savings, a project was launched by the City of Zurich. The project covers field investigations in 12 shops with different entrance types, and analytical and numerical investigations (CFD)for complementary results. The emphasis of this work was on the interaction between the situation at the entrance for different technical local solutions with other factors of importance like building ventilation, building tightness and combination with other entrances.
The results of various numerical simulations of wind induced flows through large openings in a room are presented. The study is parametric on the sizes and relative positions of the openings and the wind direction. Various grid densities have been used. Grid independency for the presented results is demonstrated. Validation of the numerical approach is performed using measurements on a test cell with a single opening. The influence of the inflow wind profile is studied. It is shown that different flow patterns are induced within the dwelling when different profiles are assumed.
For a large-scale building complex planned to be built in urban area, airflow around buildings and airflow inside a ventilated atrium of the building complex were estimated by CFO (Computational Fluid Dynamics) simulation, and wind and thermal environment were evaluated. The accuracy of CFO simulation was assessed by comparison with wind tunnel experiment. It was found that CFO tends to underestimate the air velocity near the ground surface compared with the results of wind tunnel experiment.
Results of an investigation of the effects of window position on the airflow characteristics for a typical bedroom setting in Taiwan are presented. Four different window positions were examined in the experiment which used a full-scale laboratory bedroom model with a single bed. A three-dimensional ultrasonic anemometer was used to measure airflow distribution and the results of flow measurements at two height levels are presented. Computer simulation of the airflow distribution was performed using the standard k-e turbulence model.
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