TABLE OF CONTENTS This section provides a summary of the typical design procedure for air distribution systems and a review of fundamental air distribution system design considerations. In particular, those areas where cold-air distribution design differs from "conventional" design are highlighted and discussed. For the purposes of this guide, cold-air distribution systems are defined as those that supply air at temperatures between 40 F and 50 F (4 C and 10 C). Most "conventional" air distribution designs for space-conditioning applications utilize supply air at nominal temperatures between 50 F and 59 F (10 C and 15 C).
As discussed in chapter 1, cold-air distribution is an attractive option for many space-conditioning applications. Cold-air distribution design departs from "standard" design practice in several areas. However, with the guidance provided in this document and the application of basic engineering principles, the design of successful cold-air distribution systems can easily be achieved.
The design air distribution supply temperature affects almost all aspects of air-conditioning system design. As the supply air temperature is reduced,
fan size and duct size decrease,
fan heat and fan energy decrease,
space required for fans and ducts decreases,
latent load and associated cooling energy may increase,
requirements for reheating minimum supply air quantities may increase,
cooling coil face area decreases and depth increases,
required fluid supply temperature or DX suction temperature decreases,
requirements for tempering or diffusing supply air increase, and
ventilation air fraction increases, although the absolute quantity generally remains constant.
The trade-offs among these factors must be evaluated to select the appropriate...
