**4. Conclusions**

The pool boiling performance of TiO2-water nanofluids with two different sizes of nanoparticles (4–8 nm and 490 nm) at two different concentrations (0.001 wt.% and 0.1 wt.%) was investigated on laser-textured copper surfaces. The following conclusions were made based on the results of the performed experiments:


In summary, the use of nanofluids on surfaces previously functionalized with surface treatment methods (e.g., laser texturing) was generally proved to be unable to provide an additional viable heat transfer performance enhancement.

**Author Contributions:** Conceptualization, M.M., I.G. and A.H.; methodology, M.M., K.A., A.H. and M.Z.; software, M.M. and A.H.; validation, K.A. and I.G.; investigation, A.H.; resources, I.G.; data curation, A.H., M.M. and M.Z.; writing—original draft preparation, A.H., M.M., M.Z. and K.A.; writing—review and editing, A.H., M.M. and I.G.; visualization, M.M. and K.A.; supervision, M.Z. and I.G.; project administration, I.G.; funding acquisition, M.Z. and I.G. All authors have read and agreed to the published version of the manuscript.

**Funding:** The authors acknowledge the financial support from the state budget of the Slovenian Research Agency (Program No. P2-0223 and Project Nos. J2-2486 and N2-0251).

**Data Availability Statement:** All data is available from the corresponding author upon request.

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