Presents a paper based on the research for ASHRAE research Project 551-ROP, whose objectives are to 1) determine the pressure-loss coefficients for selected HVAC fittings and compare them with data in chapter 33 of the 1985 ASHRAE Handbook, 2) extend fitting data in the Handbook and 3) provide data to establish improved test procedures for use by SPC 120 in preparing the ASHRAE standard for laboratory methods of determining flow resistance of air ducts and fittings. Discusses the performance of 11 different constructions of fittings, each with varying sizes or radii of curvature. Performance is based on zero-length dynamic losses and local loss coefficients. States the data show several differences from data published in the ASHRAE Handbook. Details these differences. Notes that additional testing is required to complete ASHRAE's database.

KEYWORDS: Research, USA, pressure drop, fittings, heating, ventilation, air conditioning, comparing, ducts, performance, bends, rectangular, orifices.