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Solidification and Melting Heat Transfer to an Unfixed Phase Change Material (PCM) Encapsulated in a Horizontal Concentric Annulus

Betzel, T. and Beer, Hans (1988):
Solidification and Melting Heat Transfer to an Unfixed Phase Change Material (PCM) Encapsulated in a Horizontal Concentric Annulus.
In: Wärme- und Stoffübertragung, 22 (6), pp. 335-344. [Article]

Abstract

The solidification and melting process of an unfixed PCM between two isothermal concentric horizontal cylinders was investigated by experimental techniques and by a combined analytical and numerical method. During the solidification process concentric solid PCM layers form at both tube walls, growing slowly into the annulus. Assuming quasi-steady heat conduction, this process is described by a simple analysis. The melting PCM reveals a different behaviour. Due to gravitational forces the solid phase moves downwards. Experiments prove that the solid retains contact with the lower part of the outer tube as well as with the upper part of the inner tube. In this process thin liquid films form between the solid body and the heated walls and heat transfer by conduction is the dominating mechanism during melting. Heat transfer by natural convection causes the melting at the upper interface. There, the melting rates, however, are comparatively small. The theoretical approach and the numerical analysis are based on a balance of the pressure forces in the thin liquid films and of the gravitational force acting on the solid material. As a result melting rates and heat fluxes may be predicted. For practical application a Nusselt correlation is derived.

Item Type: Article
Erschienen: 1988
Creators: Betzel, T. and Beer, Hans
Title: Solidification and Melting Heat Transfer to an Unfixed Phase Change Material (PCM) Encapsulated in a Horizontal Concentric Annulus
Language: English
Abstract:

The solidification and melting process of an unfixed PCM between two isothermal concentric horizontal cylinders was investigated by experimental techniques and by a combined analytical and numerical method. During the solidification process concentric solid PCM layers form at both tube walls, growing slowly into the annulus. Assuming quasi-steady heat conduction, this process is described by a simple analysis. The melting PCM reveals a different behaviour. Due to gravitational forces the solid phase moves downwards. Experiments prove that the solid retains contact with the lower part of the outer tube as well as with the upper part of the inner tube. In this process thin liquid films form between the solid body and the heated walls and heat transfer by conduction is the dominating mechanism during melting. Heat transfer by natural convection causes the melting at the upper interface. There, the melting rates, however, are comparatively small. The theoretical approach and the numerical analysis are based on a balance of the pressure forces in the thin liquid films and of the gravitational force acting on the solid material. As a result melting rates and heat fluxes may be predicted. For practical application a Nusselt correlation is derived.

Journal or Publication Title: Wärme- und Stoffübertragung
Journal volume: 22
Number: 6
Divisions: 16 Department of Mechanical Engineering
16 Department of Mechanical Engineering > Institute for Technical Thermodynamics (TTD)
Date Deposited: 26 Feb 2015 16:24
Official URL: http://dx.doi.org/10.1007/BF01387889
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