scope:

INTRODUCTION

The straight flat oval duct pressure loss tests reported in and Idem et al. (2008) were performed with the same setups as depicted by Figures 2 and 3, where the larger ducts were tested with the plenum chamber/bellmouth. The nozzle chamber was (1) not large enough for the bellmouth connection to the test duct setup, and (2) the static pressure was not adequate to be measured downstream. It is noted that upstream conical transitions into the straight duct test apparatus violated ASHRAE Standard 120, which specifies that a bellmouth be located upstream of the test section. Furthermore, the transition angles were not in compliance with Figure 20 of ASHRAE Standard 120. Likewise, ASHRAE Standard 120 requires that all straight duct pressure loss tests be conducted on test setups having an entrance length exceeding ten hydraulic diameters. This study was initiated to determine the effects of varying the inlet conditions on measured pressure loss characteristics and to establish whether the data are repeatable by comparing to the data of Idem et al. (2008).