SF-2138 -- An Experimental Study of Losses in Round Miter Elbows, Miter Tees and Capped Crosses

Space limitations often require consideration of miter elbows and miter divided flow fittings (miter tees, or bull-head tees) in a duct installation. These fittings tend to be unattractive because of their high loss characteristics and often the limited data available to the designer is based on measurements in the "low velocity" range. The purposes of this study were:

1. to determine loss coefficients in conventional miter fittings with air velocities up to 6000 fpm to compare with existing data in lower velocity ranges;
2. to investigate possible alterations in the fitting body, effects of circular arc turning vanes, and use of cascades of commercially available turning vanes to reduce losses, since little data exist in this area for round fittings;
3. to determine the loss characteristics of capped crosses ("cushion head tees") for which no available data were found, since this configuration is sometimes suggested as an alternate for miter tees.

The elbows chosen for the study (l) were of 8 inch diameter inlet and outlet. The miter tees had 12 inch diameter inlet and 8 in. outlets.