Book - School of Science and Technology

Distribution for air-conditioning 421Adjustable types – range of air patternsFixed typesFigure 15.18 Various forms of ceiling-integrated linear diffusersLine diffuserPlenum boxSupply spigotPlenum bootsto luminaireFigure 15.19 Plenum boxes for linear diffusersBottom outletsSupplyspigotof grilles distributed at intervals along the inner partition wall with ducts in the corridorfalse ceiling behind. Each inlet is equipped with a grille, so designed as to enable therequisite quantity of air to be introduced without draught.A common and effective form of grille is that known as the double-deflection type, asshown in Figure 15.20. In this form of grille there are two sets of adjustable louvres, onecontrolling the air delivery in the vertical plane and one in the horizontal plane. The vanesare usually independently adjustable by means of a special tool, and when once set are notaltered. A variety of flow patterns can be achieved according to the width of room, aspectratio and velocity.For side-wall applications, however, much use is made of the linear diffuser as illustrated,for ceiling application, in Figure 15.17. By careful selection and making use of theCoanda effect by direction of the air pattern towards the ceiling, good overall airdistribution may be achieved from such diffusers.