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Two main objectives were addressed in this article. First, a dimensionless heat-transfer correlation for single-phase flow forced convection in liquid aluminum has been derived using a novel experimental method. An aluminum sphere was rotated with a specific tangential velocity in liquid aluminum. Its melting time was measured and correlated with the convective heat-transfer characteristics. The resulting correlation has the following form:The second objective of the study was to assess the accuracy of various correlations using an annular channel, which was available at an independent setting, at the Alcan Research and Development Laboratory. The correlations investigated were those derived from the current experimental work as well as those derived by other investigators, as presented in their respective published work. Results indicated that when applied to liquid metals, theoretically derived equations as well as equations developed for fluids with a Prandtl number greater than 0.7 exhibit a very large error. As such, these equations are unsuitable for liquid metals. A considerably smaller error is exhibited by equations derived experimentally, specifically for liquid metals, thereby attesting to the careful consideration that must be exercised in the choice of correlations that are employed.This study also provides a critical assessment of various exponents used in dimensionless equations for convective heat transfer in liquid metals. While there is a general consensus that the exponent of the Reynolds number is around 0.5, the exponent for the Prandtl number varies considerably.

An experimental technique has been developed to study the convective heat-transfer characteristics of gas-agitated liquid metals. A sphere made from the same metal as the liquid metal under investigation is immersed in the center axis of the plume. The melting time of this sphere is detected, and from this time, the convective heat-transfer characteristics of the metal bath are deduced. Based on a variety of experimental results, a dimensionless correlation was deduced. This equation has the following form:Nu D ϭ 2 ϩ 10 Ϫ4.817 ϫ Re 1.556 D 2797 Յ Re D Յ 7148, Pr Ϸ 0.014 Two-phase flow and single-phase flow convective heat-transfer comparisons were made. It was found that for the same Reynolds number, the heat-transfer characteristics for two-phase flow are larger than for the single-phase flow. It was also found that the larger turbulence intensity of the twophase flow is responsible for this difference in the heat-transfer characteristics. Implications of this observation for liquid metals processing operations are discussed.

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