Improvement of Correlative Approaches for Mixed Convective Flow Through a Horizontal Vent

International audienceThis study deals with the mixed convection flow through a shallow horizontal vent linking two compartments (one over the other). Depending on the temperature difference of gas as well as the ventilation flow rate between the two compartments, the flow through the vent can be bi- or uni-directional. A literature survey highlights that three correlations are used in safety engineering to calculate these upward and downward mixed convection flow rates. Unfortunately, for the same conditions, these correlations give very different results and, to date, there is no common agreement in the scientific community to identify quantitatively the most accurate model. This study proposes a new assessment of these correlations based on new experimental data obtained from the laboratory facility as well from the industrial apparatus. In addition, an improvement of the best model is proposed which better reproduced the experimental results. © 2019 by ASME

Stereoscopic particle image velocimetry investigations of the mixed convection exchange flow through a horizontal vent

International audienceThe exchange flow through a horizontal vent linking two compartments (one above the other) is studied experimentally. This exchange is here governed by both the buoyant natural effect due to the temperature difference of the fluids in both compartments, and the effect of a (forced) mechanical ventilation applied in the lower compartment. Such a configuration leads to uni- or bi-directional flows through the vent. In the experiments, buoyancy is induced in the lower compartment thanks to an electrical resistor. The forced ventilation is applied in exhaust or supply modes and three different values of the vent area. To estimate both velocity fields and flow rates at the vent, measurements are realized at thermal steady state, flush the vent in the upper compartment using stereoscopic particle image velocimetry (SPIV), which is original for this kind of flow. The SPIV measurements allows the area occupied by both upward and downward flows to be determined. © 2017, Springer-Verlag GmbH Germany

Experimental study based on large-scale smoke propagation fire tests through a horizontal opening connecting two mechanically ventilated compartments

International audienceThis work describes an experimental study of the flow through a horizontal opening (also referred to as a vent), applicable to specific situations typically encountered in nuclear installations. The configuration consisted of two rooms, which were mechanically ventilated and connected to each other by a horizontal opening, the fire being located in the lower room. The flow was governed by buoyancy due to the heat release from the fire, inertia resulting from the mechanical ventilation, and local momentum from the ceiling jet. Two flow regimes (bi-directional and uni-directional) were encountered depending on the fire power and the ventilation set-up. This study presents 17 large-scale fire tests, investigating the behaviour of the flow at the horizontal opening according to several fire scenario parameters the fire heat release rate, the fire location, the ventilation configuration and the ventilation flow rate. This range of parameters enabled us to focus on different flow regimes, from pure natural convection (bi-directional) to forced convection (uni-directional). The new set of data obtained, based on detailed flow measurements, offers new insights for understanding the flow and developing sub-models to be used in zone codes. © 2017 Elsevier Lt