Impact of employing twisted tube with spiral V-shaped axial fins on the charging performance inside a phase change material storage: Numerical examination

Due to the reduction of energy resources and growing attention to renewable energy, latent-type thermal energy storage systems equipped with phase change materials are an effective solution for storing thermal energy and releasing it on demand. In this research, the effect of employing a twisted tube with spiral V-shaped axial fins on the melting process of phase change material in a double-pipe storage has been investigated numerically. Solving governing equations and numerical simulations were performed by the ANSYS package using the finite volume method and enthalpy-porosity technique. Water is utilized as the heat transfer fluid inside the twisted tube. The annulus space between the shell and the twisted tube is filled with RT50 as the phase change material. This three-dimensional and transient study emphasizes the effect of geometric factors, including (i) number, (ii) pitch, and (iii) height of the spiral V-shaped axial fins. The findings indicate that adding proposed fins significantly augments the heat transfer rate, which can reduce the melting time by about 32.29 %, 52.08 %, 59.38 %, and 65.42 % for single-fine to four-fins geometries, respectively, compared to the plain case (inner twisted tube without fin). Additionally, it was demonstrated that the most significant effect occurred in changing the proposed fins pitch from 100 mm to 40 mm (60% reduction), which increased the melting rate by about 32.88 %. Moreover, with a 60 % increase in height from 4 mm to 10 mm, the melting time decreased by about 61.35 %. • A twisted tube with spiral V-shaped axial fins is used in the PCM storage. • The melting process inside the proposed PCM storage is evaluated numerically. • RT50 is the PCM in annulus, and water is heat transfer fluid inside twisted tube. • The examined factors are number, pitch, and height of spiral V-shaped axial fins. • The maximum decline in the melting process was obtained by about 65.42 %.