The present study evaluated the effect Of gamma (gamma) and alpha (alpha) Fe2O3/Kerosene nanofluids for a closed loop pulsating heat pipe under the magnetic field. The nanoparticles had a size ranged from 10 nm to 30 nm. The heat transfer rate and the temperature distribution of the heat pipe were examined with and without the magnetic field. Likewise, the Fe2O3 base nanofluids were exposed to a magnetic field to measure the vapor temperature at the center of the pulsating heat pipe,directly. The results showed that both heat transfer coefficient and thermal performance of the pulsating heat pipe are enhanced by the addition of Fe2O3 nanoparticles, especially when the magnetic field is present. The increased input heat flux rises the heat transfer coefficient of the condenser and the evaporator. Lower evaporator heat transfer coefficient and higher temperature difference between condenser and evaporator were seen because of alpha-Fe2O3 nanoparticles as compared to gamma-Fe2O3 nanoparticles. Among six nanoparticles investigated in this research, the optimum type and size of Iron oxide nanoparticles under similar conditions for attaining the best heat transfer performance was 20 nm gamma-Fe2O3 nanoparticles. (C) 2016 Elsevier B.V. All rights reserved.