An investigation into the influence of wind in single-sided natural ventilation
2010-12-02T09:17:44Z (GMT) by
In the present energy and CO2 emission conscious climate natural ventilation is undergoing increasingly intensive research. Buildings located in a sheltered in-fill location subject to single-sided natural ventilation are a common occurrence. However, the combination of stack effect and wind effect induced natural ventilation rates is not well defined. This thesis investigates the influence of wind on a sheltered building subject to single-sided natural ventilation. Full-scale experiments were undertaken over a wide variety of prevailing conditions on a suitable test cell to provide the measurements for the investigation. The analysis established that the flow/pressure drop relationship representing the airflow across the boundary of the building was best described by a power law relationship with an index of n=0.6348, rather than the conventional Bernoulli equation (which reflects a special case of the power law relationship when the index n=0.5). "Warren" plots, modified to reflect the power law flow/pressure drop relationship, identified stack effect dominance for the test cell. However, the wind was shown to influence the single-sided natural ventilation rates by virtue of the wind direction altering the flow path through the openings in the building and, so, affecting the flow characteristics of the openings. The investigation enabled a prediction model to be developed whereby the natural ventilation rates in the test cell subject to single-sided natural ventilation could be predicted from internal and external temperature and wind direction. Validation of the model identified an over-prediction for high stack effect driving forces and underprediction for low driving forces. The over- and under-prediction was concluded to be the result of incorporating the flow characteristics of the building openings as constant values. The flow characteristics should be treated as a variable function of wind direction and the stack effect driving force.