The effect of inclination angle on the performance characteristic of a double-pipe latent heat storage unit

This paper presents a numerical investigation and experimental validation of the melting process of phase change material (PCM) in a double-pipe latent heat storage unit (LHSU) at different inclinations. The aim of this paper is determining the optimal inclination angle at different PCM thicknesses for the melting process in the double-pipe LHSU. The PCM is placed in the annulus while hot water flows through the inner tube. ANSYS-FLUENT 17 is used to create a transient multi-phase numerical model to simulate the thermal characteristic of the storage unit. Three masses of PCM have been numerically studied; namely 0.154, 0.308, and 0.46 kg which presents three PCM annulus thicknesses of 7, 11.28, and 14.5 mm. The length of the double-pipe LHSU is 500mm and the inclination angles are 0 degrees, 15 degrees, 30 degrees, 45 degrees, 60 degrees, 75 degrees, and 90 degrees. The numerical model has been verified through the comparison between its predicted results and those obtained from previous experimental published work. In addition, the comparison between the present experimental and numerical results shows good agreement. It has been found that the inclination of the storage unit has a significant effect on the melting behavior when the thickness of PCM is enough such that natural convection contributes to the melting process. For this condition, 45 degrees was the optimum inclination angle. Conversely, for thin PCM thickness, the horizontal orientation produced the least total melting time.

Automated summary

This study investigates the melting process of PCM in a double-pipe latent heat storage unit at different inclinations. The optimal inclination angle is found to be 45 degrees for thick PCM thickness, while the horizontal orientation is most suitable for thin PCM thickness according to experimental and numerical results.