**6. Conclusions**

Actual experiments were carried out and the results utilized as part of the analysis in the simulation part. In the simulation, the heat transfer behavior and friction factor value on the test plate were investigated for the thermal enhancement factor (TEF). TEF can be explained by the heat transfer efficiency of an impinging jet on the test plate. The optimum conditions in terms of the fluid pump power and heat transfer value could be obtained.

From the experiment and simulation results, one can conclude that the cylindrical dimpled surface enhances the TEF. The highest TEF (= 5.5) was found for the configuration with a dimple diameter of d = 1 cm, a radial dimple distance of Er = 2 d, a circumferential dimple distance of Eθ = 1.5 d, a distance between test plate and jet of B = 2, and Reynolds number of Re = 1500. The TEF which was obtained in this work was higher than that obtained in other research, which was about 4.0. This is because the friction factor ratio in this work (f/f0) was very low, even though the Nu was not different from the Nu in other work. The most suitable test plate conditions which could be used to obtain a high TEF are d = 1 cm, B = 2 d, Er = 2 d and Eθ = 1.5 d for Re=1500–14,600.

**Author Contributions:** For research articles with several authors, a short paragraph specifying their individual contributions must be provided. The following statements should be used "conceptualization, supervision, and methodology, Parkpoom Sriromreun; formal analysis, and writing—review and editing, Paranee Sriromreun".

**Funding:** This research was funded by the Research Grants of Faculty of Engineering, Srinakharinwirot University and The Strategic Wisdom and Research Institute, Srinakharinwirot University.

**Acknowledgments:** The funding of this research work is supported by the Research Grants of Faculty of Engineering, Srinakharinwirot University and The Strategic Wisdom and Research Institute, Srinakharinwirot University.

**Conflicts of Interest:** The authors declare no conflict of interest.
