Book - School of Science and Technology

Distribution for air-conditioning 427Table 15.1 Approximate sizes (mm) of air inlets (representative only)Air quantity (litre/s)Type50 100 200 300 500Perforated ceiling panels (facesize) 300 150 300 300 500 500 600 600 1200 600Line diffuser (duct size) 750 50 1000 90 2000 90 3000 90 2400 165Ceiling diffuser(neck diameter) 100 150 200 250 380(overall diameter) 330 330 450 600 860Side-wall grille double deflectiontype (face size) 200 150 300 200 450 250 450 400 660 450NoteAbove are all selected at approximately the same sound level of 40 dB.Table 15.2 Typical maximum air changerates based on a cooling differential of 10 KDeviceAir changeper hourSide-wall grilles 8Linear grilles 10Slot and linear diffusers 15Rectangular diffusers 15Perforated diffusers 15Circular diffusers 20Table 15.3 Typical maximum cooling temperature differentialsApplicationTemperaturedifference (K)High ceilinglarge heat gains/under window input 12Low ceilingair handling luminaires/under window input 10Low ceilingdownward discharge 5Floor discharge 5The 2001 edition of Guide Section B2 gives useful rule-of-thumb guidance as to both themaximum air change rates that can be achieved using various devices and as to typicalmaximum cooling temperature differentials (supply air to room) for various applications.This is used here for Tables 15.2 and 15.3, respectively.Air distribution performance (ADPI)An air distribution performance index (ADPI), a method of assessing the effectivenessof an installation to meet set comfort criteria, based upon air velocity and