Convection is one of the most important mechanisms of heat transfer. This study reflects the need to develop a heat transfer fluid which offers greater capacity than current media, achieved by increasing the thermal conductivity of the fluid. The research investigated dispersions of conductive nanoparticles or nanofluids for use in the cooling of rotational moulds. The work systematically evaluated different shaped nanoparticles dispersed into a base fluid with the aim of increasing the thermal conductivity and therefore the convective heat transfer capability of the fluid. The stability of the dispersion was probed and found to be a key parameter in determining the success of increasing the thermal conductivity of the base fluid. The convective heat transfer capability of a number of fluids was investigated, showing that, in general, the heat transfer coefficient decreased upon addition of nanoparticles. A single formulation showed a heat transfer coefficient far in excess of that predicted and was therefore used in the rotational moulding study. A mathematical model was proposed to describe the thermal conductivity of the nanofluid. Uniquely, this included the influence of the surfactant coverage on the nanoparticle surface in estimating the thermal conductivity of the fluid. The rotational moulding study used a prototype mould, developed in conjunction with the Rotofast consortium. This allowed for induction heating and liquid cooling by circulating a fluid through the inductor pipe which was in contact with the mould. CFD simulations predicted that the cooling times for water and the nanofluid should be almost identical; however, the experiment showed that the nanofluid gave a cooling time for this apparatus which was longer than water but shorter than a thermal oil.