A fixed-grid finite element based enthalpy formulation for generalized phase change problems: role of superficial mushy region

Bhattacharya, Madhuchhanda and Basak, Tanmay and Ayappa, KG (2002) A fixed-grid finite element based enthalpy formulation for generalized phase change problems: role of superficial mushy region. In: International Journal of Heat and Mass Transfer, 45 (24). 4881-4898 .

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Abstract

The enthalpy method is primarily developed for studying phase change in a multicomponent material, characterized by a continuous liquid volume fraction (phi(1)) vs temperature (T) relationship. Using the Galerkin finite element method we obtain solutions to the enthalpy formulation for phase change in 1D slabs of pure material, by assuming a superficial phase change region (linear (phi(1) vs T) around the discontinuity at the melting point. Errors between the computed and analytical solutions are evaluated for the fluxes at, and positions of, the freezing front, for different widths of the superficial phase change region and spatial discretizations with linear and quadratic basis functions. For Stefan number (St) varying between 0.1 and 10 the method is relatively insensitive to spatial discretization and widths of the superficial phase change region. Greater sensitivity is observed at St = 0.01, where the variation in the enthalpy is large. In general the width of the superficial phase change region should span at least 2-3 Gauss quadrature points for the enthalpy to be computed accurately. The method is applied to study conventional melting of slabs of frozen brine and ice. Regardless of the forms for the phi(1) vs T relationships, the thawing times were found to scale as the square of the slab thickness. The ability of the method to efficiently capture multiple thawing fronts which may originate at any spatial location within the sample, is illustrated with the microwave thawing of slabs and 2D cylinders. (C) 2002 Elsevier Science Ltd. All rights reserved.

Item Type:	Journal Article
Publication:	International Journal of Heat and Mass Transfer
Publisher:	Elsevier Science
Additional Information:	Copyright of this article belongs to Elsevier Science.
Keywords:	Phase change;Enthalpy formulation;Finite elements;Microwave thawing
Department/Centre:	Division of Mechanical Sciences > Chemical Engineering
Date Deposited:	04 Aug 2011 05:54
Last Modified:	04 Aug 2011 05:54
URI:	http://eprints.iisc.ac.in/id/eprint/38942

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