Developing flow and heat transfer in strongly curved ducts of rectangular cross-section
A numerical study of heat transfer in 90/sup 0/, constant cross-section curved duct, steady, laminar flow is presented. The work is aimed primarily at characterizing the effects of duct geometry on heat transfer by considering, especially, the role of secondary motions during the developing period of the flow. However, due consideration has also been given to varying initial conditions of velocity and temperature at the entrance section to the duct. In addition, an assessment is made of the relative contributions of individual duct walls to heat transfer in the flow. It is found that, in general, heat transfer increases with Dean number with the largest transfer rates occurring through the duct side walls and outer-curvature wall. Duct geometries with aspect ratio greater or smaller than unity have weaker secondary motions and are less effective for heat transfer. Similarly, plug-flow entrance profiles for velocity retard the development of cross-section flow thus inhibiting a significant contribution to heat transfer. It is concluded that short ducts with strong curvature and intense secondary motions can be as effective for heat transfer as longer ducts which are less strongly curved. Calcuations are based on fully elliptic (in space) forms of the transport equation governing the flow. They are of engineering value and are limited in accuracy only by the degree of computational mesh refinement. A comparison with calculations based on parabolic equations has been made and it is shown how the latter can lead to erroneous results for strongly curved flows.
- Research Organization:
- California Univ., Berkeley (USA). Lawrence Berkeley Lab.
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 5915181
- Report Number(s):
- LBL-9092; CONF-791205-11
- Country of Publication:
- United States
- Language:
- English
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