Thermofluid Analysis of Transformer Oil Flow in Transformer Oil Purifier Machine Using Computational Fluid Dynamics Approach

Abstract

Transformer oil is an essential insulating and cooling medium in power transformers, and its condition directly influences transformer reliability and service life. During long-term operation, the oil gradually deteriorates because of moisture, dissolved gases, oxidation by-products, and suspended solid contaminants, leading to a decline in both dielectric and thermal performance. Although transformer oil purifier machines are widely used to restore oil quality, the internal flow and heat transfer characteristics within these systems have not been comprehensively analyzed. Therefore, this study employs Computational Fluid Dynamics (CFD) to investigate the thermofluid behavior of transformer oil inside a transformer oil purifier machine under practical operating conditions. The numerical analysis was conducted using SolidWorks Flow Simulation 2025, which applies the Finite Volume Method (FVM) to solve the governing equations of fluid flow and heat transfer. The simulation was performed with an inlet flow rate of 2000 L/h (0.0005556 m³/s), assuming transformer oil to be an incompressible Newtonian fluid. The numerical results showed that the operating pressure varied between 98 and 108 kPa, while the maximum flow velocity reached 1.50 m/s, remaining within the recommended range for transformer oil circulation. The calculated Reynolds number of approximately 1833 indicated a laminar-to-transitional flow regime, supporting stable flow behavior and efficient heat transfer. Furthermore, the heating unit successfully raised the oil temperature to the desired operating range of 50–60 °C, facilitating viscosity reduction and improving the effectiveness of moisture removal before the vacuum purification stage. These findings demonstrate that the proposed purifier design provides reliable hydraulic and thermal performance and may serve as a useful reference for enhancing transformer oil purification efficiency, minimizing pressure losses, and optimizing future purifier designs.