## 1 Introduction
\begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Reference** & **Used Coil** & **Type of Study** & **Merits** & **Demerits** \\ \hline \multirow{10}{*}{[4]} & & & & Ice cracking is random but follows a specific pattern. When ice begins to crack, it induces centrifugal forces in the HTF, which have a stabilizing effect on the flow & \\  & & & & Ice cracking is random but follows a specific pattern. When ice begins to crack, it floods, and the heat transfer fluid that returns from the top coils, where most of the ice is gathered, tends to diminish. In contrast, heat transfer fluid in lower coils tends to rise more quickly. \\ \hline \multirow{10}{*}{[8]} & & & - Results for the case of annular fins demonstrate that the optimal operating point is calculated at a spacing of 50 mm between two neighboring fins. & The effect of annular fin spacing is quantified. More fins increase the contact surface area, which speeds up heat transfer. As the number of fins grows, more phase change materials near the tube surface will be replaced by low-heat capacity fin materials, reducing the cold storage available. \\ \hline \multirow{10}{*}{[10]} & & & - Results for the case of annular fins demonstrate that the optimal operating point is calculated at a spacing of 50 mm between two neighboring fins. & The effect of annular fin spacing is quantified. More fins increase the contact surface area, which speeds up heat transfer. As the number of fins grows, more phase change materials near the tube surface will be replaced by low-heat capacity fin materials, reducing the cold storage available. \\ \cline{1-1}  & & & - The ice production would be 21\% and 34\% greater when annular fins and rings are used compared with the bare tube. & An external melting mode may provide lower output temperatures for longer than an internal melting mode. \\ \cline{1-1}  & & & - Most ice forms when diagonal rings are used, and more ice forms while using the tube with fins. & \\ \hline \multirow{10}{*}{[10]} & & & - Conical coil melting rate was 28.32\% higher than conventional coil at 80 \({}^{\circ}\)C HTF intake temperature. & \\  & & & - Conical coils store energy more quickly than normal coils. & \\ \cline{1-1}  & & & - Faster energy storage with conical coil storage compared with regular storage. & \\ \cline{1-1}  & & & - The conical coil form was suitable for heat transmission since its base is wider than its peak. & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Merits/demerits of different shaped coils used in CTES. per fan coil, and the heat transmission rate reached 5 kW for 32 and 24 min using A9 and A14. The staggered heat exchanger provided less than 10 kW of heat when the water output temperature was 5 to 10 \({}^{\circ}\)C, which a commercial heat pump can easily achieve. [PERSON] et al. [21] studied a modified webbed tube heat exchanger using two-dimensional numerical models to improve PCM thermal energy storage (TES) performance. This heat exchanger's thermal performance was compared with webbed and triple-tube heat exchangers. Simulations monitored solidification (discharging). The redesigned webbed tube heat exchanger sped up the PCM solidification process by 41%. [PERSON] et al. [22] presented a double-pipe helical-coiled tube for containment containing latent heat thermal energy storage (LHTES) PCM. Experiments validate a 3D numerical model of PCM melting in horizontal and vertical straight double-pipe LHTES systems with the same surface area. In PCM melting, the double-pipe helical-coil LHTES performs badly. Horizontal and vertical LHTES systems must minimize PCM melting time by 25.7% and 60%. In a double-pipe helical-coiled tube, coil pitch impacts PCM melting time. So, from the review, the studies were conducted on straight tubes and ice-on-coil systems. Further, other studies concentrated on helical coil tubes with different pitches and compared the results with straight tubes.