Mixing Property and the Heat Exhaust Effect under Cross Ventilation in a Full-Scale Experimental Model

Cross ventilation is one of the most important techniques for achieving energy conservation and for
maintaining a comfortable indoor environment in hot summer periods. However it is difficult to evaluate the effect of cross ventilation quantitatively and to undertake design based on a quantitative evaluation. This is because the indoor environment is uneven and changes according to the outside conditions. It is difficult to predict the ventilation rate under cross ventilation due to the variation in wind. Hence it is still difficult to estimate indoor comfort conditions given by cross ventilation. In this paper full-scale model cross ventilation experiments are described and the properties of airflow in and around the full-scale model (velocity field, pressure distribution on surface, visualized flow pattern, heat transfer coefficient distribution, discharge coefficient of openings and so on) have been examined. The mixing property and heat exhaust effect of cross ventilation are discussed. Tracer gas concentration decay measurements were made in the
model to determine the spatial unevenness of mixing property, the air change index and the velocity
distribution. It is shown that the different mixing properties are formed according to the airflow pattern. The heat exhaust effect, was determined by using plasterboard that was set on the floor for heat storage. The temperature of the air and surface was measured, and exhaust heat by cross ventilation was calculated. The relation between temperature reduction and the flow path was examined, and the total exhaust heat by cross ventilation was compared to the total convective heat transfer from the plasterboard. These experiments showed that ventilation rate is the most important factor in determining the amount of exhaust heat and the room mean age of air. However the airflow path has an influence in the exhaust heat and mixing property in the cross ventilated space.