The heat transfer process in a power transformer establishes
the steady state temperature of the winding and core due to
the power loss in the copper. The viscosity and the thermal
conductivity of the pure fluid phase (mineral oil) together
determine the top oil temperature (TOT) and the hot spot
temperature (HST) of the transformer. In the case of a nano
fluid, similar processes take place, however, the heat transfer
is enhanced considerably. Avoiding details at this point,
certain empirical relations are given here under to estimate
the viscosity and thermal conductivity of nano fluids as
under.