Laminar-flow heat transfer downstream from U-bends
The laminar-flow heat transfer downstream from the unheated, vertical bends in horizontal U-tubes with electrically heated straight tube sections was investigated. Four U-tubes with curvature ratios of 4.84, 7.66, 12.35, and 25.36 were studied. Distilled water and almost-pure ethylene glycol solutions (water content 1 to 5%) were the test fluids. For each test section, local axial and peripheral wall temperatures were measured, and the local peripheral heat-transfer coefficients at the various locations were calculated. The experiments covered the local bulk Reynolds number range of 120 to 2500. The local bulk Prandtl number varied between 4 and 110, while the Grashof number ranged from 2500 to 1,130,000. The uniform wall heat flux ranged from 900 to 4230 Btu/hr.sq.ft (3.12 to 13.33 KW/sq.m.). This investigation permitted a better understanding of the interaction of the primary, secondary, and tertiary flow patterns. Also, a correlation was developed that predicts the heat-transfer coefficient downstream from an unheated U-bend and that can be extended to straight tubes.
- Research Organization:
- Oklahoma State Univ., Stillwater (USA)
- OSTI ID:
- 6330865
- Country of Publication:
- United States
- Language:
- English
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