Numerical investigation of influences of liquid types on flow distribution and temperature distribution in disc type ON cooled transformers

In this paper, dimensional analysis is adopted to study fluid flow distribution and temperature distribution in disc-type ON (oil natural) cooled transformer windings. Theoretical analysis on the thermal driving force and the pressure drop in the liquid circulation loop is also performed to determine the total liquid flow rate in the transformer. The thermal performance of three different liquids, a hydrocarbon mineral oil, a hydrocarbon gas-to-liquid (GTL) oil and a synthetic ester are investigated using computational fluid dynamics (CFD) simulations, based on the understanding from dimensional analysis and the flow rates determined from the theoretical analysis. It is found in the investigated conditions that the hydrocarbon mineral and GTL oil share similar thermal performance; the synthetic ester has a lower total flow rate due to its higher viscosity and therefore requires additional effort to improve the thermal performance.