Equivalent round diameter of spiral flat oval ducts

Conference · Sat Dec 31 04:00:00 EST 1994

OSTI ID:33263

Townsend, B S; Idem, S A; Khodabakhsh, F ^[1]

---

1. Tennessee Technological Univ., Cookeville, TN (United States)

Friction factors for spiral flat oval ducts were measured over the Reynolds number range 6 {times} 10{sup 4} to 6 {times} 10{sup 5}, based on hydraulic diameter. Aspect ratios ranged from 1.4 to 5.5. When plotted on a Moody diagram, the data closely followed a single relative roughness curve. It was shown that the flat oval equivalent round equation in the ASHRAE Handbook (ASHRAE 1993) is within 6.2% of a rigorous solution. Since this accuracy is within the accuracy of duct pressure loss calculations, it is recommended that the subject equation be retained for future editions of the Handbook. The absolute roughness of the ducts ranged from 0.055 mm (0.00018 ft) to 0.381 mm (0.00125 ft), averaging 0.158 mm (0.00052 ft) for the eight tests. It is therefore recommended that spiral flat oval duct be categorized as ``average`` in the ``Duct Design`` chapter of the Handbook.

• OSTI ID: 33263
• Report Number(s): CONF-9406105--
• Country of Publication: United States
• Language: English

Related Subjects

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
DUCTS
FRICTION FACTOR
PRESSURE DROP
ROUGHNESS
SPACE HVAC SYSTEMS
SPIRAL CONFIGURATION