## 4 Conclusions  
Thermal management at a high heat flux is crucial for electronic devices, and jet impingement cooling is a promising solution. Today, the efficiency of the heat sink is one of the most important parameters when designing a heat sink. High-efficiency heat sinks enhance heat transfer. This experimental study was carried out to investigate HT phenomena and the associated flow characteristics on a heat sink surface consisting of rectangular fins with a converging-diverging geometry, cooled by the air as the coolant, using multi-impingement jets on inclined surfaces. Considering the importance of analyzing the effect of the heat sink angle, nozzle diameter, dimensionless distance, and flow rate variables on the heat transfer performance of jet impingement systems, this study aims to provide scientifically proven answers to the industry. The results obtained from the experimental analysis are summarized as follows. * The experimental results revealed that the Nu increased with a higher Re. * It was calculated that the Nu increased with larger nozzle diameters. * However, it was also concluded that the Nu decreased as the dimensionless h/d distance increased, and this relationship was found to be mostly linear. * While the Nu was almost equally affected across all jet velocity levels, it was more significantly influenced at lower velocities, specifically at around 7 m/s. * Under all the inclined heat sink surface conditions examined, the Nu reached its maximum value at the flow velocity of 9.0 m/s, which corresponded to the points where the nozzle diameters and the dimensionless nozzle-to-heat sink distance ratios were at their optimum. When comparing the angle values for the same flow velocity, nozzle diameter, and dimensionless h/d distance experimental conditions, the Nus were found to be very similar. It was determined that the heat sink angle values examined compared to other parameters had less effect on heat transfer. Under constant heat flux and across all examined angle values, the highest Nu for the inclined heat sink with rectangular fins was calculated at a 10\({}^{\circ}\) heat sink inclination, with a nozzle diameter (D) of 40 mm, a dimensionless distance (h/d) of six, and a flow velocity of 9 m/s. Conversely, the lowest Nu was observed at a 30\({}^{\circ}\) heat sink inclination, with a nozzle diameter (D) of 25 mm, a dimensionless distance (h/d) of eight, and a flow velocity of 5 m/s. After examining the parameters affecting impingement jet cooling, the analyses performed according to the single variable method can provide new perspectives for the optimization of jet impingement cooling systems and offer potential improvements for thermal performance and efficiency. The next step is to carry out numerical and experimental research on the impact of the cooling effect of impinging jets using different fluids, a larger number of parameters, and under a wider parameter range, building a relevant test platform and providing more guidance and data for the application of this technology. Supervision, A.K. ; investigation, D.Y. All authors have read and agreed to the published version of the manuscript. This research was supported as a project (BAP-FYL 2021-9534) of the Research Fund of Van Yuzuncu Yil University. Not applicable. The data presented in this study are available on request from the corresponding author. The authors declare no conflicts of interest.