## 3 Results
### Inline Arrangement of the Nozzles  
Figure 5 shows the cooling process waveforms of the inline arranged nozzles with respect to the heat exchange surface of the cooler at distances of 60 to 110 mm (Figure 5a) and 120 to 170 mm (Figure 5b). The distances were varied at 10 mm spacing. The initial condition for the investigation of the cooling process was a condition where the coolant was heated to the temperature released by the thermostat to the cooler. We focused primarily on the cooling process in the cooler, which significantly affects the proper operation of the internal combustion engine. Coolant temperatures were recorded using NTC type thermistors ZA 9040-FS mounted in the inlet and outlet pipes of the cooler.  
From the graphical waveforms (Figure 5), it can be observed that the time of the cooling process is shortened by gradually increasing the nozzle spacing from the heat exchange surface. This is due to the fact that the nozzle produces a flat conical air stream. The closer the nozzle is positioned to the heat exchange surface, the less heat is dissipated from the heat exchange surface, resulting in a longer cooling process and a higher consumption of pressurized air from the storage tanks. However, the optimum cooling process occurs only when the individual compressed air streams from the nozzle outlets begin to overlap. By overlapping the air streams, the outlet temperature of the coolant decreases significantly and at the same time the consumed air from the pressure tanks is used more efficiently. This is due to the fact that a smaller volume of air with lower pressure is sufficient for the required slight temperature adjustment below the operating temperature of the coolant.  
The resulting flat conical shape of the compressed air from the nozzles also depends on the actual regulated pressure in the pneumatic circuit. As the air pressure increases, the area that the nozzle can cover increases (the angle of the air flow increases). On the contrary, when the pressure at the nozzle outlet is reduced, the area that the nozzle can cool is reduced (the angle of the airflow is reduced). It is obvious that with the type of nozzles we use (flat cone airflow) with inline configuration in relation to the cooler, there  
Figure 5: Comparison of the outlet cooler temperatures \(T_{out}\) for inline arrangement of the nozzles when varying the spacing of the nozzles from the cooler: (**a**) Nozzle spacing 60 mm to 110 mm compared to the far; (**b**) Nozzle spacing 120 mm to 170 mm compared to the fan.  
are \"empty\" spots within the heat exchange surface that are not sufficiently covered and cooled by the airflow. Despite this, the inline arrangement with an outlet pressure of 6 bar achieves a shorter cooling time from a distance of 130 mm compared to the less efficient conventional fan (Figure 5b). With increasing outlet pressure (8 bar or 10 bar) there is the potential to reduce the cooling time even at a shorter distance. At the time of 46 min, the fan cooling process reached a temperature value of 67.97 \({}^{\circ}\)C at the outlet, while the nozzles arranged inline (spacing 130 to 170 mm) reached a temperature value in the range of 63 \({}^{\circ}\)C to 65 \({}^{\circ}\)C. This resulted in a cooling improvement of approximately 5 \({}^{\circ}\)C, with the most effective cooling process observed at a distance of 160 mm (Figure 5b). Distances of 60 to 110 mm (Figure 5a) were less effective in the cooling process by 46 min compared to fan-only cooling. This is due to the short distance between the nozzles (air jets) and the cooler. The breakpoint occurred at a distance of 120 mm at 46 min, when the cooling time by fan and nozzles were equal.