Flow and thermal characteristics of warm plane air jets (measurements and predictions using different k-models)

摘要

Jets are often used for supplying air to buildings. For designing ventilation systems it is therefore of great importance to have a good understanding of air jets to avoid draught, which might lead to discomfort. At the same time as we want a good indoor climate, we also want to reduce energy consumption. The purpose of this study is to investigate the flow and thermal characteristics of warm air jets supplied under the ceiling, as a heating method, by means of numerical prediction and full-scale experiments. Together with the warm wall jet, an isothermal wall jet will also be examined. For the calculations, three different k-ε models have been used and evaluated, namely the standard k-ε the Chen-Kim k-ε model and the Renormalization Group k-ε model. The experiments have been carried out in a full-scale room where the temperature and velocity within the air jet are conducted. For the isothermal wall jet, the Chen model gives best agreement for the growth rate, while the standard k-ε model gives the best result for the velocity decay of the jet. The evaluation of the warm jet provided best results for the Chen model regarding both the growth rate and the velocity decay. The velocity and temperature profiles for the warm jet provided similar results for all models, but also some differences between the predicted and measured temperatures.