An experimental program was initiated to study the influence of test section entrance conditions on straight flat oval duct apparent relative roughness. The purpose of these tests was to assess whether deviations from test section entrance geometries as prescribed by ASHRAE Standard 120 have an impact on friction factor and relative roughness. The observed relative roughness values varied as the entrance length increased. The apparent relative roughness obtained using a test setup in compliance with Standard 120 was considerably lower than the value of relative roughness obtained with a test setup that did not conform to the standard. It is recommended that all duct and fitting pressure loss tests be conducted in compliance with Standard 120, and that Standard 120 be modified so that the flow measuring chamber velocity does not exceed 1.5 m/s (300 ft/min). It is also recommended that the entrance duct length be increased from 10 hydraulic diameters to 12 diameters.
Citation: ASHRAE Transactions, 2010, vol. 116, pt. 2, Albuquerque, NM
Product Details
- Published:
- 2010
- Number of Pages:
- 9
- File Size:
- 1 file , 3.5 MB
- Product Code(s):
- D-AB-10-001
