The objective of this work comprises the study of the thermal variables of ferrofluids (FFs) –thermal conductivity and diffusivity, and heat capacity– under applied magnetic fields for possible industrial applications, with focus in heat-transfer devices. The FFs were prepared with kerosene and Ni-ferrite nanoparticles (NPs). The NPs were synthesized by high-energy ball milling, as an alternative to the most commonly chosen NPs synthesis methods for FFs´ preparation [1]. The milling is a proper and low-cost technique for large-scale NPs´ production as up to 5g of nanometric powder can be produced in short-time and one-step procedures. The thermal variables were determined with the transient hot-wire method. The application of a magnetic field on the FFs increases the thermal conductivity and diffusivity [2] due to cooperation between the NPs, as it agglomerates them favoring chain-like and clusters formations [3]. The obtained enhancements in the thermal conductivity of prepared FFs, reach 48% in absence of magnetic field with respect of conductivity of pure kerosene and 173% for a field of 0.07T, which are in accordance of the obtained results for other systems [4]. The relative to pure kerosene thermal diffusivity was 3 at zero field and 127 under 0.07T. Also, the relative to kerosene heat capacity of the studied ferrofluids was calculated, and it was found that it decreases under the application of a magnetic field from 0.3 to 0.05. The thermal conductivity of FFs as a function of magnetic field was successfully fitted by a gas compression model considering NPs agglomerates in the fluid.