In the present work, the critical heat flux measurements were performed for the subcooled flow boiling of pure water and magnetic nanofluids (i.e., water + 0.01 and 0.1 vol.% Fe3O4) in a vertical tube. The effect of applying an external magnetic field on the CHF variation was studied experimentally as well. The obtained results indicated that the subcooled flow boiling CHF in the vertical tube is increased by using the nanofluid as the working fluid, especially in lower volume concentration of nanoparticles. The nanoparticles deposition on the tube inner surface and consequently improvement of the surface characteristics such as nucleation site density, wettability and re-wetting properties could be mentioned as the main reasons of this incident. Moreover, it was seen that applying the magnetic field leads to the additional enhancement in the CHF of ferrofluids. It could be clarified as the attraction of the nanoparticles into the magnets and increasing the surface wettability resulted in the CHF enhancement.
