Laboratory testing of flat oval transitions to determine loss coefficients (RP-1606)

Pressure loss coefficientsweremeasured for 8 converging-concentric, 15 converging-eccentric, 8 diverging-concentric, and 15 divergingeccentric flat oval transition fittings. All tests were performed in accordance with ASHRAE Standard 120-2008, Method of Testing to Determine Flow Resistance of HVAC Ducts and Fittings, except (1) the entrance duct length to the test fitting was increased to 12 hydraulic diameters and (2) the fitting loss coefficient was calculated as the slope of the linear regression of pv8 (downstream velocity pressure) versus Δp_t,_1-2 (zero-length total pressure loss of a test fitting) instead of p_v7 (upstream velocity pressure) versus Δp_t,_1-2. An Excel template file was developed to perform experimental data processing, graphical expression, and uncertainty analysis. Two pressure loss coefficient equations were developed, one for converging and a second for diverging fittings based on the experimental data. The loss coefficient regression equations will be added to the ASHRAE Duct Fitting Database, thus increasing the population of flat oval fittings.