In this study, novel longitudinal arc fns were proposed to increase the melting performance of phase change material in a
latent heat thermal energy storage device. In order to optimize these innovative arc fns, various confgurations of these fns
were designed by changing the arc length, fn angle and eccentricity of the inner tube. In order to evaluate the performance
of the new fns, fve arrangements of traditional rectangular plate fns as well as a bare tube case were also numerically simulated. In all examined cases, the volume fraction of fns was considered constant and equal to 6.13%. Consequently, the best
confguration of innovative fns was found by comparing melting characteristics of them with those of traditional rectangular
plate fns. In addition, the efects of Al2O3 nanoparticles on melting performance of some designed arc fns including the
most efcient ones were evaluated. Results revealed that the best case was able to reduce the total melting time by 96.5%
with respect to the bare tube and 67.7% with respect to 12 number of rectangular fns. In comparison with the pure PCM as
the base case, addition of 2% and 5% nanoparticles can lead to time savings of 10.44% and 12.36%, respectively.