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Handbook of air conditioning and refrigeration / Shan K

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AIR SYSTEMS: AIR DUCT DESIGN 17.33<br />

FIGURE 17.10 Rectangular elbows: (a) rectangular elbow, smooth<br />

radius, two splitter vanes; (b) mitered elbow; (c) secondary flow in a<br />

mitered elbow.<br />

vanes, as shown in Fig. 17.10a, the local loss coefficient C o is only 0.04 to 0.05. The values <strong>of</strong><br />

R o, R 1, <strong>and</strong> R 2 can be found from Table 17.11. For details, refer to ASHRAE <strong>H<strong>and</strong>book</strong> 1997,<br />

Fundamentals.<br />

For a mitered rectangular 90° elbow without turning vanes, C o is about 1.1. If turning vanes are<br />

installed, C o drops to only 0.12 to 0.18. Installation <strong>of</strong> splitter vanes in mitered elbows is also

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