“Thermomagnetic convection” is a dominating heat transfer phenomenon in ferrofluid (magnetic nanofluid). In ferrofluids, magnetic body forces induced by applied magnetic fields can produce a phenomenon similar to gravitational natural convection. If there is a temperature gradient in the presence of the magnetic field, a non-equilibrium state in the magnetization (spatial distribution of magnetization) appears in the fluid and consequently, a magnetic driving force occurs which generates flow patterns in the ferrofluid. This phenomenon is known as thermo-magnetic convection. The magnetization of ferrofluid is dependent on temperature, magnetic field, and concentration of ferroparticles. Cooler regions have enhanced magnetic properties so that the cooler fluid moves in the direction of increasing magnetic field, displacing warmer fluid and hence, thermomagnetic convection sets in. Although thermomagnetic convection is analogous to natural convection, this phenomenon is more complex and depends on various parameters like magnetic field strength, temperature and magnetic field gradient, orientation of magnetic fields, volume fraction of magnetic particles in ferrofluid, induced magnetic body force intensity and magnetization effects in ferrofluid under the magnetic field. Study of these parameters requires a solid understanding of magnetism, heat transfer, and coupling of the Navier-Stokes and Maxwell equations. In this thesis, to understand the thermomagnetic convection and effect of different above mentioned driving parameters, analytical and multi-physics computational heat transfer and fluid dynamics models are compared with experimental results. [...]