Abstarct: In this study, the flow regime and the effects of porosity and various mextal foams in boiling heat transfer in a vertical copper tube with upward flow and internal diameter of 16 mm and a thickness of 1.5 mm under constant heat flux and at atmospheric pressure by using water as working fluid was experimentally investigated. In order to ensure the correct operation of the equipment and the laboratory bed as well as validating the results of the experiments, in a single-phase and low-heat flux, several experiments were carried out and the results were compared with the existing relationships for heat transfer in single-phase mode. Which ultimately led to ensuring the correctness of the laboratory and the results of the laboratory bed. In order to compare and evaluate the effect of mextal foam On enhancement of boiling heat transfer, the experiments were performed first in an empty vertical tube - a simple tube - and then tests were carried out with similar conditions for the tube with circular mextal foam and solid mextal foam, respectively. The data from the simple tube were compared with the data obtained from the proposed relationship and their absolute deviation was reported. The foams used in this experiment were filled copper foam with porosity of 85% and a pore density of 5 pores per inch (PPI) and circular copper foam with porosity of 80% and a pore density of 5 pores per inch (PPI) with a central cavity of 8 mm. Copper foams were prepared by casting method and they were placed in the copper tube with Press-Fitting method. In this experiment, the flow regime in the two-phase mode, was in the range of the slug flow, which was detected by a glass tube at the end of the laboratory bed and a high-speed camera. Heat transfer parameters such as convection heat transfer coefficient and Nusselt number were measured at different mass flow rates and different heat fluxes and the effect of porous material, type of porosity, heat flux and mass flux on the heat transfer parameters were investigated. Finally, by comparing the results obtained from the simple tube and copper foam tubes, it was found that in low quality and in the range of mass flux from 38 to 53 kg/m2 and heat flux from 23 to 36 kW/m2, filled copper foam improves 1.5 to 1.82 and the circular copper foam can improve the heat transfer coefficient from 1.21 to 1.31 times relative to the simple tube. Also by visualization of flow regime by the high-speed camera 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 the flow, but the flow regime remains slug that in the copper foam, these slugs pass through the central cavity and in filled copper foam, they pass through foam pores.