Book - School of Science and Technology

412 Air distributionInlet at 50ºCmean room airapprox. 28ºCθ = 0ºSlot velocity = Vθθ = 30º133mmV = 4 m/sV = 12 m/sFigure 15.3 Upward air distribution from low level side-wall outletsDownward systemIn this type of system the air is introduced at high level and exhausted at low level, as inFigure 15.4. It is commonly used with full air-conditioning where, due to the air admittedbeing cooled, it has a tendency to fall. The object of distribution in this case is so to diffusethe inlet that the incoming air mixes with room air before falling. Thus, the inlets shown inthe diagram as discharging downwards, in practice deliver in part horizontally at sufficientspeed to ensure that the air completely traverses the auditorium. Turbulence is thuscaused with the desirable effect already mentioned. On a smaller scale, as applied to anoffice building, this system appears as in Figure 15.5Provided the height of room is not abnormal, the extract opening may be at high levelas in Figure 15.6. Short circuiting is avoided by the velocity of the inlet air carrying over tothe far side of the room. Another possible arrangement is a variation of this, namely,`downward±upward', as in Figure 15.7(a).Supply fromplantCentral plenum chamberMultiple diffuserat ceilingExtract fromunder steppingsSeparate supplyto organ gallery(not shown)Figure 15.4 Downward air distribution in a concert hall