CFD Study on Thermal Performance of Radiators in a Power Transformer: Effect of Blowing Direction and Offset of Fans

A focus on the present numerical study is on the fan air flow-used in the oil natural air-forced cooling system of a 25-MVA power transformer. An experiment is done to benchmark the present simulation methodology for the fan. Thermal performance of a radiator assembly is studied in two parts: 1) effect of horizontal and vertical blowing direction of two different fans at two speeds and 2) the effect of offset of one of the fans blowing in the horizontal direction. Vertical as compared to horizontal blowing is less efficient in dissipating heat from the radiator assembly considered here, as more air gets wasted from the sides. This is in contrast to the commonly encountered results of a heat exchanger-a cross instead of counter-flow heat exchanger is more efficient. The effect of offset of the top and bottom fan increases the heat dissipation. The factor of merit is proposed as a performance parameter to compare the different cases, considering the benefit in terms of heat transfer and cost incurred in terms of power consumption of the fan. Computational fluid dynamics are used more as an analysis than a design tool and lead to an improvement in the design of the radiator fan assembly.