The present study explores experimentally the process of melting of a phase change material (PCM) in cylindrical geometry. The study is performed with a commercially available paraffin-type material with the melting point of about 28 degrees Celsius. The experiments are conducted using vertical tubes of four different diameters, filled with the PCM and immersed in a water bath. In each tube the experiments are performed at the water bath temperatures of 10, 20 and 30°C above the melting point of the paraffin. The tubes are transparent, and the melting process is monitored and recorded by a digital camera. Each tube is thermally insulated at the bottom, and at its top open to atmosphere, to allow free expansion of the melt liquid. The digital pictures of the melting process were analyzed, and the results were graphically presented as melt fraction vs. time, showing for the plain tubes the effects of tube diameter and temperature difference. Numerical simulations are performed in order to provide an insight into the mechanisms governing the process. Generalization of the results is attempted based on the dimensionless groups, including the Fourier, Stefan, and Rayleigh numbers. A correlation connecting the melt fraction with these dimensionless groups is suggested.

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