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Melting in phase-change thermal storage media
- "The research performed under the auspices of DOE Contract EY-76-S-02-2993 is described in this report. The various research tasks were aimed at obtaining fundamental and applied results for the melting process which occurs when energy is added to a phase-change thermal storage medium. Four research tasks were undertaken, encompassing both experiment and analysis and extending over a range of phase change temperatures from 80 deg. to 244 C (176 to 471 deg. F). The studies dealt with horizontal and vertical tubular heat sources embedded in the phase medium. Results were obtained for the heat transfer coefficient at the heated surface and for the size and shape of the melt region created by the phase change process. The heat transfer coefficients provide a measure of the temperature difference required to drive a given heat flux into the storage medium, while a knowledge of the size and shape of the melt region facilitates a rational positioning of a multi-element heat source array. Aside from specific quantitative results for the heat transfer coefficients and for the melt region size/shape, the research has produced a global finding of considerable practical importance. Both the experiments and the analysis have shown that aside from an initial period during which conduction is important, the dominant heat transport mechanism for the melting process is natural convection. This finding stands in contrast to the heretofore standard model whereby it was assumed that conduction was the only transport mechanism. The dominant involvement of natural convection means that the temperature differences that are required to drive heat into the melting solid are very much less than those which are characteristic of pure conduction transport. Therefore, in practical terms, the melting portion of the storage/extraction cycle appears to be less critical with regard to temperature difference than is the freezing process which occurs during extraction."
- "Melting in phase-change thermal storage media"@en
- "Melting in phase-change thermal storage media"