## 3 Results and Discussion
### Effect of Operating Parameters  
3.2.1. Influence of Flow Rate  
The charging and discharging characteristics of the bio-inspired TES tank have also been accessed by varying the HTF mass flow rate. The HTF was pumped into the TES tank at three different mass flow rates: 1.5 kg/min, 3 kg/min, and 6 kg/min. However, the operating temperature range was maintained constant for all flow rates. The charging characteristics of the bio-inspired TES tank under three distinct mass flow rates are shown in Figure 7. The PCM sensible heat component (solid phase and liquid phase) and latent heat component are encompassed within the temperature window. Early in the charging cycle, Figure 7 illustrates a notable temperature differential between the HTF inlet and HTF outlet because the PCM was at a low temperature (15 \({}^{\circ}\)C) during the initial stages of the charging cycle and absorbed most of the heat transported by the HTF. Nevertheless, regardless of the HTF mass flow rate, the temperature difference between the HTF inlet and outlet remained fairly constant during the phase change process. Following the phase transition process, the temperature differential diminished and approached zero because the heat was only absorbed as sensible heat by the liquid PCM. Figure 7: \(Cont.\)  
Figure 7 also shows the power transferred by the bio-inspired TES tank during the charging cycle. There was an apparent fluctuation in the power transferred by the TES tanks early in the charging cycle. This is because, prior to the commencement of the charging cycle, the HTF confined in the tubes of the PCM tank was at the same temperature as the PCM. An abrupt heat transfer occurred when the hot HTF entered the tank during the charging cycle and caused a substantial temperature difference between the HTF inlet and HTF outlet. This irregular power profile reached a consistent state when all of the cold HTF that was held in the TES tank was completely removed, accompanied by a notable rise in PCM temperature. The power transferred by the TES tanks approached a constant value during the phase transition, and then it started to decline during the post-melting stage. The rate of heat transfer during the phase transition is significantly affected by the mass flow rate of the HTF. The power profile of the TES tank remained consistent across different HTF mass flow rates despite variations in magnitude. Figure 7 clearly shows that the TES tank with the HTF mass flow rate of 6 kg/min had the largest power output of between 175 W and 250 W during the phase transition process. Figure 7: Variations in power, PCM temperature, and HTF inlet and outlet temperatures with respect to time at three distinct HTF flow rates: (a) 1.5 kg/min, (b) 3 kg/min, and (c) 6 kg/min during the charging cycle. A comparison was made between various HTF mass flow rates and the amount of time needed for the PCM temperature to increase from 15 \({}^{\circ}\)C to 29 \({}^{\circ}\)C. It came to light that the HTF mass flow rate correlates directly with the time. With a 6 kg/min HTF flow rate, the bio-inspired TES tank approached 29 \({}^{\circ}\)C in the least amount of time (0.47 h) across all the flow rates. However, with flow rates of 1.5 kg/min and 3 kg/min, it took 0.52 and 0.49 h to reach 29 \({}^{\circ}\)C, respectively. The discharging characteristics of the bio-inspired TES tank under three distinct mass flow rates are depicted in Figure 8. The figure makes it clear that, during the initial stages of the discharging cycle, there was a substantial temperature differential between the HTF inlet and HTF outlet since the PCM was at a high temperature (45 \({}^{\circ}\)C) during the initial stages of the discharging cycle. However, regardless of the HTF mass flow rate, the temperature difference between the HTF inlet and outlet remained fairly constant during the phase change process. Following the phase transition process, the temperature differential diminished and approached zero because the heat is only released as sensible heat by the solid.