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A coupled heat and mass transfer model of pure metal freezing using comsol multiphysics.

Pearce, J V (2013) A coupled heat and mass transfer model of pure metal freezing using comsol multiphysics. AIP Conf. Proc., 1552. pp. 289-294.

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Finite element simulation is a well established technique for simulating melting and freezing behaviour of metals. However, because most methods rely on simulating the phase transition using an empirical method which models the latent heat with a peak in the temperature dependence of the heat capacity, the temperature range of melting/freezing of the material is necessarily large. For pure metal fixed points, the melting range is of the order of 0.1 mK and alternative means of modeling the phase transition are required. In this study, Comsol Multiphysics is employed to simulate the freezing of a zinc fixed point for standard platinum resistance thermometer (SPRT) calibrations. The liquid-solid interface is represented by the boundary of an adaptive mesh whose geometry adjusts itself to accommodate the propagating liquid-solid interface. This means that the temperature range of freezing can be arbitrarily narrow. The evolution of the mesh as a function of time is determined by the thermal conditions. The transport of heat and impurities, particularly at the liquid-solid interface, is modeled simultaneously and the concentration of impurities in the liquid volume is evaluated as a function of time and location. Because this is a coupled simulation the influence of impurity distribution on the liquid-solid interface temperature can be characterized. Some results of the model are presented against the background of impurity effects on the freezing curves of ITS-90 fixed points. A new method of determining the endpoint of freezing of experimental data is shown and used to compare the model with measurements.

Item Type: Article
Keywords: SPRT, impurity, Scheil, modelling, modeling, freezing, fixed-point, fixed point
Subjects: Engineering Measurements
Engineering Measurements > Thermal
Identification number/DOI: 10.1063/1.4819555
Last Modified: 02 Feb 2018 13:14
URI: http://eprintspublications.npl.co.uk/id/eprint/5951

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