Age-of-the-air in rooms according to the environmental condition of temperature: A case study

•Convective strengths prevail with respect to the direction imposed on the air inlet.•Changes in age of the air depend on the flow pattern established by the temperatures.•The interchange of the energy causes the room average age not to change significantly.•CFD tools are very useful for the study of the airflows in rooms. The ventilation air in rooms is generally kept moving due to a constant difference in pressure. This gradient is generated through a general ventilation system (hybrid or mechanical), with minimum ventilation flow being established by the normative. However, there are cases in which, even if the established flows are fulfilled, certain indoor areas exhibit an excess or shortage of ventilation. The excess or deficit depends on the flow pattern that the air follows in the room, and its characterisation is possible using the indoor local and mean calculation of the age of the air. The flow pattern of air is conditioned by the energy transfer processes; therefore, analysis of air's behaviour under two extreme situations (summer and winter) was performed to compare the results with a previous isothermal model. For the development of this work, a double study (numerical and experimental) was conducted. The numerical calculations were developed using a CFD tool, which is notably useful for this type of research work.