A Novel Method for Experimental Investigation of the Paraffin Unconstrained Melting Based on Image Processing Technique and Comparison with Numerical Results

Based on experimental evidence, the presence of thermocouples in solid phase change materials affects the results and changes the melting regime from unconstrained melting to constrained melting. In this study, a new method for direct measurement of liquid mass fraction of phase change materials during melting was proposed based on the image processing technique. In this method, images of the melting process are prepared in controlled conditions at successive times. By performing image processing techniques, the boundary of the solid core is determined and the enclosed surface area is calculated and divided by the initial surface of the solid phase. This method was applied to unconfined paraffin melting inside a horizontal cylinder. The problem was also numerically simulated by the multi-phase method (VOF) and the change in the total volume of paraffin (total volume of solid and liquid phases) due to the difference between solid and liquid density was taken into account. A good agreement between numerical and experimental results was observed. The shape and sizes of the solid core in the experimental images and the numerical results at different times match well.