Experimental study on thermal buoyancy-induced natural ventilation

It is well known that natural ventilation is caused by the outdoor wind velocity and the indoor-outdoor temperature difference. Generally, natural ventilation is rarely caused by one effect alone, but by the coupled form of two effects. However, only the indoor-outdoor temperature difference (ΔT) was considered to evaluate the characteristic of thermal buoyancy-induced natural ventilation in this experimental study. The indoor-outdoor temperature differences were set to 5, 10, 20 and 30 °C. The measured ventilation rates by changing ΔT were compared to the calculation results based on the hydrostatic theory. From the experimental results, it was found that the ventilation rate is exponentially proportional to ΔT and the area ratio (AR) of the inlet opening to the outlet opening is an important factor to affect natural ventilation. However, the influence on a ventilation rate by AR nearly disappeared when AR exceeds over 5.0. In addition to it, it was identified that AR and a flow resistance coefficient of Cd for ventilation can be correlated as an exponential function and its form is exp(−3.6AR).