**6. Patents**

Polish patent number: P.415828, "Two-phase thermosiphon heat exchanger", date 16-08-2018.

**Author Contributions:** Conceptualization, M.Ł. and G.G.; Methodology, M.Ł.; Software, M.Ł., A.N.G., and A.R.; Supervision, G.G.; Visualization, G.G., D.A., and B.W.; Writing—original draft, M.Ł., G.G., and M.K.; Writing—review and editing, A.N.G. All authors have read and agreed to the published version of the manuscript.

**Funding:** Research funded by the National Centre for Research and Development, research project LIDER (grant no. *LIDER/08/42/L-3/11/NCBR/2012*) "Intensification of the heat transfer process in innovative heat exchanger—investigation with the utilization of PIV method".

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