Numerical Simulation And Approach Of Downward Directed Vertical Wall Jets And Air Lake Phenomena

The primary objectives in HVAC design are to provide thermal comfort and acceptable indoor air quality for building occupants. With more demands on comfort and better interior air quality, displacement ventilation has come into use in many occasions as one better air-flow organization form. According to principle of displacement ventilation, supplying air from air diffuser at bottom of room is the best strategy. However, it is impossible to arrange air diffuser at bottom of room in some occasion. There is Professor Zhao Hongzuo and Li Angui' s suggestion: based on Coanda effect of air jet to side vertical wall and the air pool phenomenon , can supplying fresh air from ceiling to floor achieve similar indoor environment of displacement ventilation?Based on the idea above, CFD method was used to discuss the performances of factors to downward directed vertical wall jets (DDVWJ) further. To ensure the feasibility of the final conclusions, flow visualizing experiment is contrasted with the numerical prediction.There are many factors that influence the effect of downward directed vertical wall jets. The paper established the computational model of DDVWJ .Study was performed to achieve the performance of DDVWJ when only one parameter varied. The conclusion of this paper show that, when the vertical distance between ceiling air diffuser and side wall is small enough, DDVWJ can supply fresh air from ceiling to floor and induce "air lake" phenomena above floor. When the distance becomes larger, such similarity will decrease dramatically. As to the small velocity, coanda effect can generate as the air outlet velocity varies. When the velocity becomes larger, the degree of coanda effect reduces. But the entrainment capability of the jet increases, the domain of the jet becomes larger. When the air outlet temperature rises, the degree of the coanda effect increases too. The smaller tuyere, the better coanda effect. For the cool jet, as the room size or roughness becomes, the coanda effect becomes too. But the argument is small, coanda effect can generate too.