Simulation of airflow distribution in rooms by systemic and multidimensional approaches
Titre du congrès :AIHce - VENT 2006
Ville du congrès :Chicago
Date du congrès :13/05/2006
In order to achieve a satisfactory level of hygiene in industrial workplaces and to assess pollutant transfers, it is necessary to control the airflow distribution. Two different approaches are presented for evaluating air distribution in a real ventilated room of 2,300 m3 volume: the first one uses Computational Fluid Dynamics tools (CFX, FLOVENT); these codes are based on the resolution of Navier-stokes equations and are widely used in many fields but suffer from a lack of qualification, especially in the field of ventilated rooms. The second approach is an intermediate one between predictive numerical simulation and experimental determination of aerodynamic parameter; it is the systemic approach. The main features of the IDTS code developed and based on the principles of the systemic approach are presented. A model is built from a combination of elementary systems representing basic flows as piston, mixing flow, recirculation, short circuiting; each elementary system is characterized by specific parameters, such as the residence time and the volume of the unitary system. The adjustment of the model is derived from the comparison of the responses to a signal injected into the model with a tracer emission realized at the room inlet. This response depends on the internal fluid flow patterns and is called the residence time distribution (RTD). The difficulty is in finding the most representative adjustment and the associated parameters. The experimental results obtained on the ventilated enclosure (particularly the RTD curve) are compared with the CFD simulations and the IDTS identification, and are overall in good agreement. Finally, the objective of this presentation is to increase public awareness of the potentialities of both approaches but also of their limits, especially about the gaseous transfers in a ventilated indoor space.