Study of an Air Conditioning System Using Air Masses

Part 1 -Examination of Continuously Produced Vortex Rings by CFD

Abstract

Generally, in a large space, a nozzle-type outlet is used as the outlet of an air-conditioning unit. However, most of the air flow from the outlet is dispersed and lost before reaching the target point. The air flow that the target point is only a part of the original. Moreover, in terms of heat-transport as well as airflow, cold air or warm air will diffuse before reaching the target point. Therefore, only some cold air or warm air can reach the target point. On the other hand, a vortex ring has high mass and momentum transporting capability. The compact and unchanged characteristic of vortex rings is suitable for obtaining high-density distribution of the transported fluid within a specific confined region. In this study, the aim was to produce vortex rings continuously, and apply them to an air mass utilizing their high heat-transport capacity to realize ductless ceiling-air-conditioning in a large space. We describe the behavior of a series of vortex rings showing how they behave compared to single vortex rings. The examination was performed by using computational fluid dynamics (CFD). In the study, the jetting speed and the volume of one shot were used as parameters. Accordingly, we found the following. 1) When the vortex rings are repeatedly produced, the arrival distance of the second and subsequent vortex rings become short. Therefore, it is necessary to devise for extending the range of a vortex ring. 2) Increasing the jet velocity tends to increase the reaching range of the vortex rings and the heat-transport range. 3) When the jet velocity increases, the turbulence on the transfer course of vortex rings becomes strong, and the vortex ring cannot maintain a stable state. 4) Even if the volume of jet in each time is reduced and the frequency of vortex ring generation is increased, the reaching range of the vortex ring and the heat-transport range scarcely change. 5) If the volume of jet in each time is reduced, the trailing surplus air decreases and the behavior of vortex rings becomes stable.