CFD ANALYSIS OF AIR-CONDITIONING BY MOVABLE NOZZLE-TYPE SUPPLY AIR OUTLETS INSTALLED HORIZONTALLY

Abstract

When planning the thermal environment for an indoor area, it is critical to avoid uneven air flow distributions in the occupied zone and to ensure the conditioned air is uniformly circulated in the room. It is also essential to avoid generating cold drafts that may cause occupants to experience unpleasant chilliness. For these reasons, when air conditioning a large space it is common practice to employ a horizontal supply diffusing device that supplies air parallel to the ceiling from upper sections of the walls. In most horizontal supply diffusing devices, nozzle outlets with air long throw are commonly used. It is important to determine an appropriate supply velocity and an appropriate temperature difference between the nozzle temperature and the occupied zone temperature in order to appropriately control the thermal environment of rooms. We have proposed a movable nozzle-type supply air outlets method in which the supply direction varies periodically as a means of controlling the terminal velocity in the occupied zone by increasing the diffusion area of the air flow without reducing the throw. A previous report compared the conventional outlet design guideline and the movable nozzle-type supply air outlets method by assuming the outlet is installed on the ceiling. It is confirmed that it is possible to constitute a comfortable occupied zone by adopting the movable nozzle-type supply air outlets to a large room by calculating the air diffusion performance index (ADPI). In the present report, the characteristics of the movable nozzle-type supply air outlets method are analyzed by assuming that the nozzle outlet is on the wall and by using an unsteady simulation based on a CFD simulation. The ADPI is used in the thermal environmental evaluation of the occupied zone in a similar manner as the previous report. However, in this present report, the effect of drafts in the occupied zone is additionally evaluated using the draft rating (DR) that calculates the effect of drafts in the occupied zone based on the air flow velocity and the occupied zone temperature.