Computer aided synthesis of RTD models to simulate the air flow distribution in ventilated rooms

In order to achieve a satisfactory level of hygiene and comfort in ventilat ed premises and to assess the pollutant transfers, it is necessary to contr ol the air flow distribution. An intermediate approach between predictive n umerical simulations and experimental determinations of aerodynamic paramet ers characterizing air distribution in rooms, is constituted by the systemi c approach. This article presents the main principles of this approach, whi ch is based on the residence time distribution (RTD) theory, commonly used in chemical engineering, and gives an illustration of its potential extensi on to ventilation problems. The aim of the IDTS code developed is to build a model from a combination of elementary systems representing basic ideal f low patterns (perfect mixed flow, plug flow,...). The adjustment of the mod el ties in the comparison of the response to a stimulus injected into the m odel with an experimental tracer emission performed in a ventilated room in let. The general solving strategy adopted, consisting in a two-level dissociated treatment of parametric identification and structural identification of mo dels, is first presented. Then, two problems tackled during the qualificati on step of the IDTS code are presented to illustrate the applications of th is computer-aided design tool for the description and the quantification of air flow patterns and the associated pollutant transfers observed in venti lated indoor spaces, and particularly in nuclear ventilation networks. The comparison between experimental residence time distribution curves recorded in two ventilated laboratory enclosures and the simulated ones shows good agreement. For the last illustrative problem, a comparison with results obt ained from a computational fluid dynamics tool has been performed. (C) 2001 Elsevier Science Ltd. All rights reserved.