Numerical modelling of the natural ventilation of underground transformer substations

► A model of natural ventilation of underground transformer substations is developed. ► Simulations serve to analyse air flow patterns and temperature distributions. ► There is a component of reverse flow in the outflow grilles. ► There is a mass of static warm air at the top part of the switchboards zone. ► Correlations for air mass flow rate and heat transfer coefficients are proposed.