Abstarct: The boiling heat transfer, especially the subcooled flow boiling, is one of the cooling systems being used in industries due to their high heat transfer coefficient. The subcooled flow boiling happens when the bulk flow temperature and the interface temperature are lower and higher, respectively than the saturated temperature corresponding to the flow pressure. One way to increase heat transfer is through high porosity mextal foams in the channel, which have a large surface area relative to the volume, increasing heat as well as heat transfer. The present study has experimentally investigated the porous effect on subcooled flow boiling in a vertical annulus tube with inner diameter of 50.7 mm and outer diameter of 70.6 mm, by providing an open-loop experimental setup. The tube is filled with 10 PPI open-cell nickel mextal foam. The effects of different parameters such as heat flux, mass flow rate (ranging from 0.012 to 0.0286 kg/s), and the inlet subcooling temperature (i.e., 35–50℃) on heat transfer coefficients are explored. The theoretical relations also validate the heat fluxes in the subcooled boiling regime. The results revealed that increasing the heat flux leads to an increase in the subcooled flow boiling heat transfer coefficient. The heat transfer coefficient is a function of mass flow rate for a given heat flux. In the subcooled boiling heat transfer zone, the wall temperature remains almost constant, and no significant changes were observed in the experiments. Hence, if the mass flow rate decreases in this zone, the bulk temperature will be increased while the wall temperature is constant. Also, the subcooled heat transfer coefficient increases with a decrease in inlet subcooling temperature. Using 10 PPI nickel porous inside the annular tube, the subcooled boiling heat transfer coefficient can be increased up to 30% compared to an empty tube.