Methodology for the Evaluation of Natural Ventilation in ... - Cham

external and internal airflow patterns in wind tunnel and test chamber environments. In addition,the limits of achievable Reynolds numbers for models of small scale are of concern.4.1.3 Experiment FluidsIn building ventilation modeling, several different fluids have been used in scale models toreplicate fluid flow phenomena. Most work has been completed using water, salt water, or air asthe working fluid. Each fluid has its own particular characteristics, which can influence the scaleof the model used and the resulting flow patterns.With water as the modeling fluid, smaller scale models are sufficient, often on the scale of 1/20 thto 1/120 th . Water modeling techniques have been used extensively in experiments to understandfluid flow in naturally ventilated spaces. Water models are nearly always constructed of clearPlexiglas, which allows the flow patterns to be easily seen and captured on film. Two types ofwater models are used at present for evaluating buoyancy driven flow; heated water models andsalt-water models. The heated water models require a heat source to drive the buoyancy flow,with the small-scale mock-up immersed in a large ‗ambient‘ tank. The model is placed right sideup in the tank, allowed to reach steady state, then measurements are taken. There is little to noheat loss through the walls of the model constructed of Plexiglas and with the relatively small(