Visualization Of The Airflow Patterns Of 12 Typical Diffusers And Experimental Investigation On The Turbulent Coefficient

The primary objectives in HVAC design are to provide thermal comfort and acceptable indoor air quality for building occupants. There are many factors that influence the short- and long-term success of HVAC systems in meeting these and other objectives. One such factor is the performance of the air diffusion equipment and the associated air distribution systems within a particular building. Proper air distribution is important to achieve satisfactory thermal comfort and air quality in the occupied regions of ventilated rooms. Airflow patterns and distribution of velocity, temperature, and turbulence intensity in ventilated rooms are primarily determined by the diffuser air jets and its mixing with and entrainment of room air. Therefore, understanding the characteristics of diffuser air jets and their relations to the airflow conditions in the occupied regions is essential for the selection of diffuser location.Under the financially sponsored by the National Nature Science Foundation of China and the Key Laboratory of Beijing, airflow patterns of the twelve typical diffusers outlets jets are visualized, and the pictures about their nonisothermal jets are taken. Based on the analysis of these pictures, the characteristics about these diffusers jets airflow patterns are discussed. One of these results is that the patterns of diffusers jets are decided by the parameter at exit and the perpendicularly distance to the ceiling. When the exit velocity is less, the jets cannot attach to the ceiling, and project to the occupied region indirectly, and the patterns will be bell. And as the ceiling configure is grid suspension ceilings, the same jets patterns can be achieved. For the downward-projected wall jets, the capacity that the jets attach to the wall is affected by the distance or the angle between the slot diffuser and the wall, and the parameter at the exit.The turbulent coefficient is one important parameter which mark the configuration of the outlets and the parameter at exit. Based on the study and analysis of the datum of other researchers, the conclusions clarify again that the configuration of the outlet and the parameter at exit has significant effect on the turbulent coefficient. And for one outlet, its turbulent coefficient varies with the parameter at the exit. And for isothermal jet, its turbulent factor decreases with the exit velocity increasing. For nonisothermal jet, its turbulent coefficient increases with the absolute value of the Archimedes number decreasing.