Performance assessment of multi-tube inline and staggered array based latent heat storage system

In this article, the charging and discharging characteristics of a shell and multi-tube latent heat storage system are investigated numerically to select a suitable array type for the multiple heat transfer tubes. This study considers nine tubes in eight different arrangements. Numerical simulations on simplified two-dimensional paraffin wax domain were performed using ANSYS Fluent. The results are depicted as contours and streamlines to visualize the progress of melting and solidification. The transient performance is evaluated based on the variation of liquid fraction, heat transfer rate at tube surfaces, melting time, and amount of energy stored with time. The results show that the rate of melting and energy storage performance depend greatly on the configuration of tubes. The staggered array with high tube pitch to tube diameter ratio (PR) cases reported better performance. By changing the arrangement of tubes, a 74.2 % reduction in melting time is observed for the staggered array with PR = 3.5, i.e. S3.5 case, as compared to the inline array with PR = 2, i.e. I2 case. By changing the arrangement of tubes, a 9 % improvement in the amount of energy stored is achieved for the S3.5 array compared to the I2 array for 300 min of charging. Unlike melting, solidification is governed by conduction thus for the same value of PR, the solidification time was almost the same for the both inline and staggered arrays. Higher PR cases performed faster solidification, and about 56 % reduction in solidification time is observed for PR = 3.5 as compared to PR = 2 cases.