CH-12-036 -- Laboratory Testing of Saddle-Tap Tees to Determine Loss Coefficients PDF

Pressure loss tests were conducted on diverging and converging flow saddle-tap tees per ASHRAE Standard 120 (ASHRAE 2008). A power law curve fit was used for diverging flow tees to correlate branch loss coefficients as a function of branch-to-common flow rate and area ratios. Likewise, a logarithmic curve-fit model was used to correlate branch loss coefficients for converging flow tees as a function of branch-to-common flow rate ratio. The argument of the logarithmic function was adjusted to account for the area ratio of the fitting. For both diverging and converging flows, main loss coefficients were correlated in terms of an inverse linear relationship with the straight-to-common flow rate ratio. Main loss coefficient data were largely independent of branch-to-common area ratio. The resulting coefficient of determination values ranged from 0.543 to 0.927, indicating a suitable degree of correlation.