Characterisation of ventilation rate in naturally-ventilated buildings using heat dissipation from a line source

• Velocity studies were done with a line heat source covering the whole aperture.
• A study to investigate buoyancy effects for the entire opening was done.
• Well-mixed zone concept was used to give insight on flow parameters.
• Estimation of model parameters was done using data-based mechanistic approach.

To determine air exchange in naturally-ventilated buildings, Eren Özcan, Vranken, and Berckmans (2009) used heat dissipation from a heat source close to an inlet to measure ventilation rate through the opening. Because their method used a bulky heat source, which caused an obstruction to airflow, they were unable to cover the whole of the inlet opening, and therefore, an improved technique was required. This study extended the earlier method to investigate heat dissipation by using a line heat source that covered the whole vertical extent of the inlet. Steady state experiments were performed with a constant heat source, and dynamic experiments, where the heat source was turned off during the ventilation process. A two-dimensional temperature distribution around the ventilation opening was obtained by infrared thermal imaging. Using data-based mechanistic approach, well-mixed temperature zones were used to predict the volumetric concentration of fresh air supply, and to investigate the effect of buoyancy on the heat plume. Results obtained revealed that ventilation rate can be predicted using data-based mechanistic approach with an error of 8%.