Heat transfer coefficient is a key parameter for efficiency evaluation of heat exchangers. Good stability and high heat transfer coefficient are essential for the application of nanofluids in heat exchangers and solar systems. In this work, nanofluids with good stability were prepared, and the influence of vertical magnetic field on flow and heat exchange of magnetic nanofluids under laminar and turbulent conditions was mainly studied. The flow and heat transfer rules of Fe3O4 nanofluids with or without magnetic field conditions, magnetic field strength, magnetic field distribution, the nanoparticle concentration and nanofluids temperature were systematically studied by setting up an experimental platform. The results show that the intensity and distribution of magnetic field had a significant influence on the heat transfer of magnetic nanofluids, whether in laminar or turbulent flow. When the magnetic field strength is 800G and 1000G, the convective heat transfer coefficient increases by an average of 23.89% and 26.12%. However, the influence of magnetic field on its flow characteristics is not obvious, and the effect on resistance coefficient increases by only 2.01%. In addition, the characteristics of magnetic nanofluids also have a certain influence on its flow and heat transfer. When the temperature of magnetic nanofluids is increased, the convective heat transfer coefficient will increase. When the concentration of magnetic nanofluids is increased, the pressure drop will also increase, but it has little effect on the drag coefficient.
