**5. Conclusions**

An investigation on the flow boiling of refrigerants R134A and R410A in two enhanced surface tubes and one smooth tube was carried out. The effects of flow pattern, mass flux, and saturation temperature on the boiling heat transfer were discussed. A comparison between experimental data and predictions calculated by several existing correlations for in-tube evaporation was conducted. The main conclusions can be summarized as follows:


**Author Contributions:** Conceptualization, Z.-C.S. and D.J.K.; data curation and investigation, Z.-C.S., W.L. and X.M.; methodology and formal analysis, W.L. and D.J.K.; project administration, L.M.; resources and

visualization, D.J.K.; funding acquisition, W.L. and L.-X.M.; writing—original draft preparation, Z.-C.S. and X.M.; writing—review and editing, D.J.K. and Z.-C.S. All authors read and approved the final manuscript.

**Funding:** This work was supported by the National Science Foundation of Zhejiang Province (LY19E060004).

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