Abstarct: In engineering studies, the issue of heat transfer and its improvement, as well as the design and production of dense heat exchangers has always been of great importance. In this regard, it can be said that mextal porous materials as a type of material structure allow the design and production of dense heat exchangers and improve heat transfer. Also, considering that the study on flow boiling was at the beginning and most of these studies were also carried out on horizontal flow boiling, therefore, research in this field and the development of related relationships require more data. For this reason, the main focus of this study is on the vertical boiling flow using a simple tube and copper foam tube. In the present study, the flow regime and boiling heat transfer was experimentally investigated in a vertical copper tube - down to up flow- with an internal diameter of 16 mm and a thickness of 1.5 mm under constant thermal fluxes and at atmospheric pressure by using the water as working fluid. In this study, in order to validate the results and to ensure the accuracy of the sensors and the laboratory bed, several experiments were performed in the single-phase, and the results were compared with the existing relationships for single-phase heat transfer, which indicates the accuracy of the experimental setup. In two-phase regime, the experiments were performed in an empty vertical tube-simple tube-and the mean absolute deviation of the test data and the existing proposed relationships was compared and reported. Then, in order to compare with the simple tube, the experiments were repeated in the same conditions for the vertical tube containing copper foam; In this study, a copper mextal foam with a porosity of 85% and a pore density of 5 pores per inch (PPI) was used which was made by casting method and was put in a copper tube using press-fitting method. All two-phase experiments were in the slug flow area and were visualized by a glass tube which placed the end of the test section. In this study, the convection heat transfer coefficient were measured in different heat and mass fluxes for both simple tube and tube with copper foam. Also the effect of the porous material, heat and mass fluxes on the heat transfer mechanism were investigated. Finally, the comparison between the simple tube and tube with copper foam showed that in low quality and in mass fluxes 38 to 53 kg/m2s and heat fluxes from 23 to 36 kW/m2, Copper foam makes a tangible decrease in wall temperature, which, due to constant thermal flux, improves the heat transfer coefficient from 1.5 to 1.82 times (in tube with copper foam relative to simple tube). Also, with visualization at the end of the test section, it was found that the use of mextal foam -due to the structure of the foam- created a disorder in the shape of flow which makes it difficult to detect the flow pattern; But despite this disorder, the flow pattern was still recognizable and in this experiment it became clear that despite the use of mextal foam, the flow pattern remains slug and mextal foam does not change the flow pattern.