Book - School of Science and Technology

420 Air distributionconnections to the diffusers being of flexible ducting, thereby providing dimensionaltolerance between the duct and the terminal position. To ensure that air distribution iseffective, the room is divided into approximate squares with one diffuser to each. Alternatively,if it be necessary to use a non-symmetrical spacing, segments of diffusers may beblanked off to avoid, for example, impingement of high velocity air flow at walls whichwould otherwise create excessive air movement at the occupied level.Swirl ceiling diffusersOriginally used more in industrial applications to introduced large volumes of air, swirldiffusers are now used in many comfort air conditioning solutions and ranges of smallerdiameter diffusers have been developed. The design of the diffuser produces a swirlingrotational type of discharge of the supply air creating a high level of induction and a rapidreduction of temperature difference. At the same time the noise levels are also low. Invariable volume application the diffusers, because of the high induction, will maintaingood performance down to about 25% of maximum duty.The layout and integration of the diffusers with false ceiling arrangements is similar toother ceiling diffusers described previously. Figure 15.16 shows a typical arrangement.Linear diffusers ± ceilingFor use in open plan offices and in avoidance of interference with ceiling pattern, the lineardiffuser in many different forms is commonly used. In its original form, Figure 15.17, it wasan adaptation of the continuous side-wall grille but took advantage of the Coanda effect.Development of this type of diffuser takes many forms, as shown in Figure 15.18. Asmay be seen, facilities are available for adjustment of the air flow pattern. Individualsections of the continuous length are supplied by means of air plenum boxes which may,in turn, be integrated with luminaires as Figure 15.19.Side-wall inletsWhere there is no false ceiling or other means of introducing the air through ceilingdiffusers, it is necessary to adopt single wall inlets, these usually taking the form of a seriesSuspensionPlenum boxFigure 15.17 Multi-vane type linear diffuserDiffuser