Influence of source geometry on plume development

This thesis report describes an experimental study of thermal plume development in a confined, ventilated environment. These conditions are encountered in displacement ventilation facilities. Experiments were conducted in a 5.6 m high ventilation test cubicle with a 4.8 x 4.2 m2 floor area. Heat sources used were a 1 m diameter cylinder comprising 5 sections of identical area (4 identical superposed cylindrical surfaces and a top disk) and a rectangular source comprising four 0.25 x 1.5 m modules, in which only the top surface was heated. These experiments involved measuring temperatures and velocities in the absence of stratification. Following an extensive appraisal of the new metrological system comprising a data acquisition unit, which measures simultaneously velocities using 16 thermo-anemometric probes and temperatures using 64 thermocouples, we describe the experimental results obtained for both cylindrical and rectangular sources. The aim was to study the influence of source geometry on the laws governing plume development. We therefore studied the following parameters for each source configuration: plume centre position and velocity, temperature difference between plume centre and exterior, plume shape and elliptical radius at different heights above the source. These parameters were obtained by applying the Gaussian elliptical model to the experimental temperature and velocity measurements. Furthermore, we also compared the plume virtual origin position and flow rate for different source configurations and we investigated the influence of source geometry on these parameters. We could thereby draw up theoretical laws governing the plume virtual origin position with respect to the heating height for the cylindrical source and with respect to the source width for the rectangular source. The plume virtual origin position is very important for calculating plume flow rates and designing collection systems. Moreover, the different measurements taken enabled us to check theoretical point and linear source models for the different study cases. A temperature and velocity measurement error calculation is given for each configuration; this provides us with the error in plume elliptical radius, flow rate and virtual origin position.