Numerical simulation and optimization of ventilation and heat dissipation in main transformer room of semi-indoor substations

Abstract

The semi-indoor substations have gained widespread application in urban areas due to the compact footprint and low maintenance costs. However, the unique structural characteristics and operational circumstances present significant challenges on the heat dissipation. This study employs the computational fluid dynamics (CFD) simulations to investigate the ventilation and heat dissipation in the main transformer room of a 110 kV semi-indoor substation. The novelty of this study lies in the integration of dynamic solar radiation modeling and air inlet optimization in the semi-indoor substations. By integrating real-time variations in solar radiation intensity employing user-defined function (UDF), this study provides a dynamic model that better reflects the transient thermal behavior of substations. The effects of air inlet angles on velocity distribution, temperature distribution, and airflow rate are evaluated. The results demonstrate that an air inlet angle of 30° reduces transformer hot spot temperatures by 1 K and surface temperatures by 3 K compared to conventional 60° designs, while increasing airflow rates by 18 %–22 %. Smaller angles (15°–45°) amplify turbulence-driven cooling but intensify temperature fluctuations, whereas larger angles (60°–90°) stabilize thermal distribution at the cost of 30 %–35 % airflow reduction. Dynamic solar modeling identifies peak cooling demands at 14:00, aligning heat dissipation strategies with diurnal radiation patterns. These findings establish a validated approach for optimizing passive cooling in urban substations, balancing efficiency and stability under transient conditions.