| Feature | 1994 Database | 2009/2021 Database (Fundamentals) | |---------|---------------|-------------------------------------| | Format | PDF + DOS software | Web-based calculator, Python libraries | | Fitting count | ~200 | ~350+ | | Reynolds correction | None | Re-dependent C for Re < 10^5 | | Roughness sensitivity | None | C = f(ε/D) for certain fittings | | Compressibility | None | Correction factor for ΔP > 2000 Pa | | Data uncertainty | Not reported | ±5% for common fittings, ±15% for complex tees |
The database implicitly assumes galvanized steel with absolute roughness ε = 0.09 mm (0.0003 ft). For flexible duct or internally lined duct, no modification is given—engineers must add separate friction loss. 5. Comparison to Modern Databases (2009, 2021 ASHRAE) The 1994 edition has been superseded, but its influence persists. duct fitting database -ashrae 1994- pdf
| Table | Fitting Type | Key Parameters | C Range (Typical) | |-------|--------------|----------------|------------------| | T1 | Elbows, 90° Smooth Radius | r/D (radius/diameter) | 0.15 – 0.30 | | T2 | Elbows, Mitered | Number of segments | 1.0 – 1.5 | | T3 | Tees, Converging (Flow into main) | Area ratio, Flow ratio | 0.2 – 4.0 | | T4 | Tees, Diverging | Branch angle (30°-90°) | 0.5 – 6.0 | | T5 | Transitions, Sudden Expansion | Area ratio (A1/A2) | 0.8 – 1.0 (loss factor based on upstream velocity) | | T6 | Transitions, Sudden Contraction | Area ratio (A2/A1) | 0.1 – 0.5 (loss factor based on downstream velocity) | | T7 | Conical Reducers | Included angle (α) | 0.05 – 0.30 | | T8 | Branch Entries (45°, 90°) | Heel vs. Throat radius | 0.4 – 2.5 | | T9 | Damper, Opposed Blade | Blade angle, % open | 0.2 (full open) to >20 (nearly closed) | | T10 | Silencers (Packless) | Length, flow path | 1.5 – 4.0 | | Feature | 1994 Database | 2009/2021 Database
[ C = \frac\Delta P_measured0.5 \rho V_ref^2 ] Comparison to Modern Databases (2009, 2021 ASHRAE) The