## 3 Results  
In the context of the designed simulation for natural gas compression, the process begins with natural gas entering the compressor from the pipeline at a pressure of 15 bar. The simulation details the compression stages: in the first stage, the gas is compressed to an average of 30 bar, followed by a second stage where it is further compressed to 75 bar. The third stage's final pressure is variable, depending on the set pressure and volume of the storage tanks being filled. Before any optimization is applied, the storage tanks are pressurized as follows: low-pressure (LP) tanks are set to 130 bar, medium-pressure (MP) tanks to 205 bar, and high-pressure (HP) tanks to 250 bar. Notably, all three types of storage tanks have an equal volume of 2400 L and initially contain gas at a pressure of 15 bar. The pressure variations during the compressor's initial operation are illustrated in Figure 7.  
After each compression stage, the natural gas is cooled with water using an intercooler. The temperature difference before and after intercooling is shown in Figure 8. The intercooler reduces the gas temperature by an average of 35 \({}^{\circ}\)C at the exit during the first and second stages and by approximately 22 \({}^{\circ}\)C at the end of the third stage. The equal-volume storage tanks take approximately 54 min (3211 s) to reach the set pressure. The filling times for each tank are as follows: LP takes 13 min, MP 19 min, and HP 22 min. The pressure and temperature variations during the filling process are illustrated in Figure 9a,b. Figure 8: Temperature differences before and after intercoolers of the stages in the compressor. Figure 7: Pressure measurement at the stages in the compressor. During the filling process, the storage tank temperatures rise, with the LP tank reaching 55 \({}^{\circ}\)C, the MP tank 73 \({}^{\circ}\)C, and the HP tank 82 \({}^{\circ}\)C. Once filling is complete, heat dissipates into the surrounding ambient air, which is at 20 \({}^{\circ}\)C, gradually lowering these temperatures. The 24 h monitoring period begins with the compressor filling the empty storage tanks. Once the tanks reach full capacity, the compressor shuts down and the vehicle tanks are refueled using a dispenser. Three vehicle tanks are selected for this process. While one vehicle tank is being filled, the other two are discharged and reset to an initial pressure of 5 bar at ambient temperature. The total number of vehicle tanks filled within the 24 h period is recorded. The vehicle tank filling process follows a staged approach. It begins with LP, which initiates the transfer. As soon as the pressure difference between LP and the vehicle tank reaches 10 bar, MP is activated to continue the process. Once MP reaches the same 10 bar pressure difference with the vehicle tank, HP takes over and completes the filling process, bringing the vehicle tank pressure up to 200 bar. After each vehicle tank is filled, the system waits approximately 60 s before initiating the next filling cycle. The 10 bar pressure difference between the storage tanks was chosen as a design parameter to ensure a sufficient mass flow rate is maintained throughout each phase of the filling sequence. This value is not a fixed standard and may vary depending on station layout, storage tank configuration, and operating objectives. In this study, it was selected to guarantee continuous flow without stagnation, particularly during the high-demand fast-fill process. The model allows this threshold to be easily modified, enabling its application to various design or operational scenarios. During refueling, LP is excluded from the process if its pressure drops to 55 bar, and MP is excluded when it falls to 130 bar. At this point, the next stage begins. If HP drops to 205 bar, the compressor is activated to refill all storage tanks in sequence, starting with LP, followed by MP, and finally HP. The pressure variations within the system follow a specific range. LP and MP operate with a pressure range of 75 bar, while HP operates within a 45 bar range.