A 3D numerical model of an ONAN distribution transformer

Abstract

The aim of this work is to validate a numerical model used to simulate the natural convection in a distribution transformer. The transformer of interest is of the oil natural air natural (ONAN) type and the model seeks to obtain the temperature and velocity fields in the oil volume. The simulation domain reproduces a slice model developed for a previous experimental study. In the numerical model, the heating element, which consists of a series of parallel heating channels, was simplified into a permeable medium. The numerical study was carried out by applying the Finite Element Method to solve the 3D Navier-Stokes and heat equations using the in-house developed Par-GPFEP code. In order to validate the model, the numerical results obtained from the simulations were compared with the experimental measurements obtained from the existing experimental device (Cordoba et al., 2018). Despite the simplifications in the numerical model we found a satisfactory overall agreement between numerical and experimental results, both in heat transfer rates, temperature distribution and overall flow patterns. The simplification of the heating element causes differences in the behavior of the thermal plume immediately above it, but the effect seems to be local and not to affect significantly the overall convective flow.