Short-Term Airing by Single Sided Natural

Under cool climate conditions buoyancy driven single sided natural ventilation is very effective and can provide high air change rates for ventilation and IAQ control, but frequently severe concerns arise with regard to local discomfort caused by cold drafts. The purpose of the work is to develop design procedures for the evaluation of airing performance in terms of ventilation characteristics and to define optimal control strategies for the integrated HVAC-window systems that assure a satisfactory IAQ and an acceptable thermal comfort. In order to deepen the knowledge of the transient thermal and fluid dynamic phenomena that take place in a single-side natural ventilated enclosure when only indoor-outdoor temperature differences are present, a suitable laboratory test rig was developed to perform extensive experimental analysis of the phenomenon under controlled and repeatable conditions. The transient air flow rate within the first ten minutes of an opening period was measured by a new developed tracer gas method and by measurements of velocity profiles in the opening The trivial action of opening a window gives rise to a phenomenon which is complex to analyse, and which is influenced by the various boundary conditions in a way that is not yet fully understood. A number of simple analytical/numerical models are available for the analysis of airing by window opening, but its transient behaviour in terms of air change rates, air temperature and ventilation efficiency is not taken into account in a satisfactory way. In the project results from calculations by simplified ?engineering? models and by a transient CFD model are compared with laboratory measurements for different cases. The project is funded through the Hybrid Ventilation Centre Aalborg University and performed in cooperation with Politecnico di Torino , Italy .   Project duration: April 2003 ? April 2005 Persons: Per Heiselberg , Marco Perino