## 1 Introduction
The total refrigeration capacity of the installed set-up was 172 kWh. The solidification process (charging) has been investigated for different inlet temperatures and mass flow rates of the heat transfer fluid. Fastest charging tests showed the lowest energy consumption. A comprehensive experimental study was presented about both solidification and melting processes in an internal melt ice-on-coil cold storage system by [PERSON] et al. [7]. The influence of some operational parameters including the inlet temperature and mass flowrate of the heat transfer fluid were investigated in both charging and discharging processes. A shell and tube type latent cold storage system was considered: liquid water flows in the shell, while ethylene glycol is the HTF in the tube side. An electronic ice thickness measurement method was used to monitor the solid-liquid interface variations during the phase change. Experimental results showed that, for both solidification and melting processes, natural convection was the dominant heat transfer mechanism after a short heat conduction dominated period. [PERSON] et al. [8] studied the phase change phenomena around a horizontal tube in a cold thermal storage system and based on the experimental results, investigated the effects of different heat transfer fluid (HTF) inlet temperatures on the ice formation. [PERSON] [9] experimentally investigated the growth rate of ice on cooled copper tubes. He found that the axial growth rate of ice is different at low values of the coolant Reynolds number and small freezing times. Also, he found that ice on the bends is thicker, that is attributed to internal flow disturbances of the coolant, and the formation of local eddies inside the bends. [PERSON] et al. [10] compared experimentally the influence of adding Al\({}_{2}\)O\({}_{3}\) nanoparticles to either distilled water as PCM or to a mixture of aqua ethylene glycol (50 wt.%) as an HTF on the performance of the cold storage system. Results concluded that adding the nanoparticles as nucleation agent to PCM alone is much more beneficial to cool the storage system than adding it to the HTF alone. [PERSON] et al. [11] presented a compound cold storage system that combines a heat pipe-based seasonal ice storage system with a chilled water storage system. The seasonal ice storage system automatically charges winter cold energy in the form of ice. In summer, the stored ice is extracted for cooling, and then the melting ice is used as a chilling medium for chilled water storage. Results showed that the appropriate combination of the two types of cold storage can greatly improve the applicability of the seasonal cold storage and reduce the life-cycle cost of a building cooling system by 40%. In the experimental and numerical research conducted by [PERSON] and [PERSON] [12], the influence of different coolant flowrates and temperatures were studied during the charging process of an ice-on-coil ice storage system. Their investigations showed that for the ice formation, the temperature changes in the coolant is much more influential compared to the flow rate variations. Besides the experimental studies, there are some numerical works, which analyzed the charging or discharging process of the ice storage system. [PERSON] et al. [13] simulated the charging and discharging processes of an internal melt ice-on-coil thermal storage system using Simulink. Their relatively simple model provided acceptable qualitative results about the heat transfer. The results indicated that by increasing the coil diameter, heat transfer, and accordingly the thermal efficiency increases. However, the heat resistance increases simultaneously. [PERSON] and [PERSON] [14; 15] performed numerical simulations to study the influence of the material, thickness, and arrangement of the thin layer ring on the performance of an ice storage system. The Taguchi method was used to achieve the optimal results. The results indicated that the type of material and the arrangement of the thin layer ring have the most significant effect on the ice formation.