AT-78-05-2 -- Balanced Duct Systems

For the past decade, Sargent and Lundy have been designing coal storage ventilationsystems using computer-aided duct design methods. Our computer program is notuniversal, but rather a series of smaller programs. This gives us the flexibilityto economically analyze and design portions of systems, modify programseasily, add and update fitting loss coefficients as data becomes available,evaluate balancing techniques, and determine the effect of fittings on theoverall resistance of a system.

The major effort during the early development of these programs was thesearch for fitting data, and the subsequent correlation for computer use. Oneshould note that Chapter 31, Air Duct Design, of the 1977 ASHRAE Handbook ofFundamentals has been revised extensively and includes a greatly expanded sectionon fitting data. Now that fitting data and computer algorithms are readilyavailable, the use of computer-aided duct design should increase. Is the developmentof computer-aided duct design a worthwhile investment? To help you judgefor yourself, this paper presents a philosophy for designing duct systems utilizing computer-aided techniques. Specific examples compare the effect of alternate fitting configurations and design methods on the total system resistance and balancing requirements for a bunker ventilation system. While the examples presented herein are based on a specific type of system, the conceptsare applicable to any type of duct system.

Citation: ASHRAE Transactions, Volume 84, Part 1, Atlanta, GA



Product Code(s): D-AT-78-05-2