A new parameter for assessment of the cooling rate of metallic moulds—Concept and practical implications
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Abstract
The cooling (or heating) rate of the metallic mould is of fundamental importance as it controls the rate of extraction of the latent heat of solidification, and consequently the morphology and the properties of the casting. Its evaluation is, however, difficult because it is both position-and time-dependent. In this study, a new parameter has been developed to assess the cooling (or heating) rate of the mould as an entity. This physically meaningful parameter, which is based on Kondratyev's regular regime theory, is characterised by its universality (as it can be calculated or measured for moulds of various geometric forms) and its constancy (as it is both position- and time-independent over a period of the transient process). In the present paper, Kondratyev's theory is extended to the case in which the change in the enthalphy of the body and the combined convective and radiative heat losses are not necessarily equal in magnitude. An approximate closed-form solution for the relationship between this “mould cooling rate constant” and the process variables is developed for a spherical mould of a uniform wall thickness, using the heat balance integral method. Available experimental data were used to confirm the validity of the concept of the mould cooling rate constant and to demonstrate its practical implications.
Keywords
Metallic moulds Temperature distribution Cooling rates Spherical coordinates Convection Heat transferPreview
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