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Chung, T.H.;Kim, S.J.;Lee, B.C.;Kwon, S.S.
- Solar Energy
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- v.8 no.2
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- pp.66-72
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- 1988
Natural convection in a horizontal annulus with spacers has been studied on the effects of diameter ratio and Rayleigh numbers and position of spacers by experimental method. In case of vertical spacers, the local spacer Nusselt numbers show positive values on the lower spacer, but negative values on the upper spacer. In case of horizontal spacers, the local spacer Nusselt numbers show positive values on the upward surface of spacer, but negative values on the downward surface of spacer. The mean tube Nusselt numbers and mean cylinder Nusselt numbers with vertical spacer are increased 10% and 2.1%, respectively by those of horizontal spacer.
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Kang, Myeong-Gie
- Transactions of the Korean Society of Mechanical Engineers B
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- v.35 no.3
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- pp.237-244
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- 2011
An experimental study was carried out to investigate the effect of the inclination angle on the nucleate pool boiling of saturated water at atmospheric pressure. We considered an annulus with a gap of 5 mm and a bottom opening. The inner tube of the annulus was heated, and the outer diameter and the length of the tube were 25.4 mm and 500 mm, respectively. The inclination angle was varied from horizontal to vertical. The results were compared to those for an annulus with a larger gap and a single tube. In the small-gap annulus, the effect of the inclination angle on the heat transfer was not significant. However, an early onset of the critical heat flux was observed at 80 kW/$m^2$ when the annulus was horizontal. Liquid agitation and bubble coalescence were considered to be the major heat-transfer mechanisms.
https://doi.org/10.3795/KSME-B.2011.35.3.237 인용 PDF KSCI

Yoo Joo-Sik
- Journal of computational fluids engineering
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- v.4 no.2
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- pp.1-8
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- 1999
Natural convection in a horizontal annulus with the inner cylinder heated by the application of a constant heat flux and the isothermally cooled outer cylinder is considered, and the transition of flows and the bifurcation phenomenon are numerically investigated for air with Pr=0.7. The zero initial condition always induces a crescent-sheped eddy flow. A bicellular flow in which the fluid descends along the vertical central plane of the annulus can be obtained at high Rayleigh number by introducing artificial numerical disturbances. Dual solutions are found above a certain critical Rayleigh number. Hysteresis phenomena have not been observed.
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