Experimental and numerical investigation on the effects of cooling method and fan configuration on the thermal performance of panel-type radiators for transformers

To reveal the performance differences and underlying mechanisms of transformer panel-type radiators under different cooling methods and fan configurations, this study takes a PC1800-22/460 panel-type radiator as the research object. A high-fidelity three-dimensional fluid-thermal coupled simulation model was established, capturing the low-velocity oil flow dominated by oil channels structures and the non-uniform annular jet characteristics of the axial fan, while comprehensively accounting for the complete heat transfer pathways involving thermal convection, conduction, and radiation. The model accuracy was validated on a 110 kV transformer temperature-rise test platform, and the flow and heat transfer distribution laws of the radiator under Oil Natural Air Natural (ONAN) and Oil Natural Air Forced (ONAF) cooling modes were revealed. The results show that the oil flow distribution is governed by the geometry of the oil channels; ONAF enhances heat dissipation solely by increasing the air-side convective heat transfer coefficient without altering the internal oil flow characteristics. Although increasing the fan diameter improves heat dissipation, it leads to a sharp rise in energy consumption. In contrast, increasing the fan installation distance exhibits a significant diminishing marginal effect, with heat dissipation gains rising markedly at first and then tending to saturate. A Merit Factor was proposed to balance heat dissipation gains against energy consumption. Based on this metric, a fan diameter of 600 mm combined with an installation distance ≥140 mm is identified as the optimal operating condition that reconciles excellent thermal performance with operational economy.