Numerical simulation of transient effects of window openings.

The simulation of room airing (ventilation by means of door/window opening) by means of CFD techniques requires a specially skilled user, because a number of difficulties arise since the first stage of simulations development, when the user is asked to choose the calculation domain and the time step, and choices which in principle appear correct may frequently lead to meaningless results. This work is centered on the 20, transient analysis of a single side enclosure where the ventilation is only due to temperature differences. Wind effect has not been taken into consideration. Different runs have been performed varying: boundary conditions, window sizes and calculation domains. Field model results have been compared to lumped parameter and zone model analyses. A check on conservation principles has shown that CFO results are affected by noticeable inaccuracies for what concerns the prediction of both air temperature and ach's, which may be partially overcome re-scaling the time dependence of the phenomenon.