Experimental Study On Characteristics Of Up-fixing Diffusers And Space Air Distributions Of Displacement Ventilation

Since up to 90% of a typical person's time is spent indoors and building energy consumption is increasing, indoor air quality and energy saving are increasingly recognized in recent years. Therefore, displacement ventilations (DV) are being recognized and used gradually by designers in China as a means of ventilation to provide good IAQ and save energy. DV systems give rise to not only better air quality and saving energy, also larger room-average ventilation effectiveness than traditional mixing systems. Therefore, its use has been extended to ventilation in offices and other commercial spaces, in addition to air quality , comfort is an important consideration in the world. In domestic, displacement ventilation has been increasingly used in industrial applications and in comfort spaces.Displacement ventilation systems have many advantages, such as providing better IAQ and save energy. But also has many disadvantages, small heat loads can be removed without draft problem and large vertical temperature differences can cause draft problem, for example. DV systems can not be used widely just for these disadvantages. So that many people have taken all kinds of ways and measures to use and develop these techniques of DV systems.Firstly, according to the disadvantages of DV systems, the measure of difiusers being fitted above the occupied zone of DV systems is presented in this dissertation. In this way, the space between difiusers and the occupied zone is enlarged. The supply air flow out at a somewhat higher velocity and then reaches the floor. And along the supply air jet, the room air in the occupied zone is induced into the supply air and is mixed, then the primary supply air temperature is decreased and the cooling capacity of DV systems is increased. The face of difiusers is reduced correspondingly. However, the supply air reaches the floor at a somewhat higher velocity, too. But above all, the supply air to the floor is more perpendicular. This permits a virtually perfect distribution over the floor surface at the same time as impact losses cause a somewhat reduction of velocity and an increased admixture of room air to the primary air. Every ventilation system introduced on market first has to be very carefully analyzed regarding advantages as well as disadvantages. The limitations of the Up-fixing Difiusers of DV(UFDDV) system have been very clearly indicated in the dissertation.In order to realize the up-fixing difluser of DV system, special conditions based on advantages and disadvantages of the UFDDV system have been brought forward in the dissertation. And then characteristics of the supply air jet of the UFDDV system were analyzed by using the theories of jet and useful mathernatic formulae of the diffusers were obtained originally, which the outlet air velocity distribution was uneven. Since then, the experiment founded on special conditions and nozzle outlets for the selecting form of diflusers was carried out, and the satisfying form of the UFDDV diffusers was picked out Where after, based on the front experiment, the rectangle difluser structure fitting characteristics of the UFDDV conditions was designed, and the characteristics experiment of it has been also carried out Useful mathematic formulae and parameters of the supply air velocity and structures for difiusers were ascertainedAt last, based on the results of these front experiments and these characteristics of the UFDDV system, the dissertation has presented the design process for up-fixing difluser of DV systems. And men using the design process, an experiment model has been designed and measured. The parameters of the model spaces were obtained. And the thermal comfort was analyzed and evaluated by using the experiment data. The results obtained from analyzing the experimental data shown that the up-fixing difluser of DV system was feasible and some useable conclusions were educed.