Experimental follow-up and understanding of indoor airflow in buildings – FLUBAT

The method is based on the 3D Lagrangian tracking airflow by injection of substance tracers in buildings. The Lagrangian tracking for different occupied areas will allow understanding the interaction between the air diffusers and the ambience. The 3D Lagrangian approach has been the subject of a CETHIL thesis which has validated the principle. Now, we expand the approach to a wider area by using more cameras for tracking tracers and accordingly modifying the algorithms. This is an important issue in terms of technological barriers. In a second step the method will be applied to a set of relevant ventilation cases for low energy buildings. The air diffusion test chamber of LaSIE (AIRDIFF), equipped with means of diagnosis by laser anemometry, will host different reference scenarios. The anemometry laser systems will serve for the validation / calibration of the Lagrangian method. We can draw conclusions about the interactions between the flows generated by the air diffusers and the ambiance itself from different reference cases and, thus, provide important information to open new ways for development of modeling methods. In parallel, it will be possible to provide operational information which will be processed and edited by the project partner society CIAT. This information will especially permit the determination of the conditions for successful implementation (with respect to comfort and air quality) of innovative air diffusers.

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The buildings of tomorrow will be, at least, energy-saving Buildings. The important reduction of the necessary powers in this type of buildings raises the crucial problem of the spatial distribution of the low flow rates of air which we will have to be injected in the rooms of life. The air quality and the thermal comfort will be strongly threatened if the problem of the mixture of the air injected into the ambient air is not effectively controlled. A typical finalized technological solution which allows a consequent improvement of the mixture was proposed within the framework of the project ANR-PREBAT 2005 "INDUBAT". It will be of use as base to this project. It is about an innovating diffuser with high induction based on the passive control of the mixture of the jet air in the ambient air. This is obtained, in particular, by the use of original geometries integrated into the conception of the diffuser. As for the other devices, the performance is qualified in Laboratory, in configuration of free and isothermal jet today what is not a common situation in the building. In a realistic building situation, the qualification of the driving flows is inevitably going to ask the question of the interaction between the jet and the room in which is going to develop a 3D low speed flow. Furthermore, the coupling air jet / internal thermal flow field is hardly qualified while the control of the ambient conditions underlies an effort in the direction of a control of the driving flow. The absence of an effective tool of diagnosis of the in the room makes then difficult the analysis of the performance of these new technologies in real situations.
To remedy it, we suggest developing a new experimental means of characterization of the 3D internal thermal flow field: a 3D tracking of particles (3D Particle tracking Velocimetry) by using different types of cameras to obtain a description of the whole dynamics in the room, so allowing the qualification of innovative solutions. The second stage of this project will consist in exploiting the 3D PTV in the case of the diffuser. The aim is to understand the interaction of the jet of this diffuser with the room. A set of 12 configurations of injection will be analyzed, producing a knowledge which will be given to the simulation community working in the field of the thermal of the building.