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Energy cost of fans used in air duct systems can account for 15-20% of electrical energy used in commercial buildings (this figure is even higher in industrial buildings). Building energy costs can be reduced considerably if air duct systems are designed for the least life-cycle cost. There exist a number of air duct design methodologies. However, most of them rely largely on heuristics and seldom take into consideration prevailing local economic conditions. The recently developed T-method addresses most of these shortcomings. Although the T-method is a life-cycle cost optimization procedure, it requires the condensation and expansion of the system. For very large systems, this may introduce complications. In this paper, an approach to air duct system design that does not require the condensation and expansion steps of the T-method is suggested. This procedure comprises three stages-initial sizing, pressure augmentation, size augmentation (S). As a consequence of the approach, the Enhanced Friction Chart and Diameter Chart, which explicitly incorporate cost information, are also developed. These charts can be used as guides in duct sizing.

Units: Dual

Citation: ASHRAE Transactions, vol. 106, pt. 1