Abstract
A detailed numerical investigation has been carried out here about a heat storage system inclination effect on the phase change material (PCM) melting process in order to comprehend the natural convection mechanism inside a shell and tube thermal energy storage (TES) unit. This unit is filled by Rubitherm organic material (RT35) which has a low storage density. Distilled water is used as heat transfer fluid (HTF,) that circulates downwardly inside the tube to melt the PCM which contributes to acquire a storable thermal energy. Based on the enthalpy method, two dimensional numerical method has been employed to analyze this process which has shown a good numerical predictions against the experimental results. Several unit positions were examined to interpret physically the thermal demeanor of the fusion process in terms of; heat transfer modes estimation, PCM melting rate, axial and radial temperatures distribution. The obtained results clarify that the TES unit inclination according to the range angles [0-90 degrees] makes an imbalance of the natural convection in the PCM liquid fraction which contributes to create an instability and diminution of the heat transfer during the melting process. Moreover, the vertical unit state was the favorite position to the heat transfer recirculation inward the PCM.