Heat Transfer Study in Oil Channels of a Power Transformer Winding ONAN Cooling System with and without Insulating Paper Based on Numerical Modeling
In this study 3 geometry for ONAN cooling system of power transformers are numerically simulated with (Perforated nomex) and without insulating papers (Netting tape). Geometries are A, RA, and R type. The A type has just axial channels. The RA type has radial and axial channels but there are no baffles to drive the flow into radial channels. The R type is like the RA type but with baffles. Insulating paper used in this study has some holes to cause some vortex in flow to increase heat transfer. The CFD code used is Fluent 6.3. To simulate flow in natural convection mode, Boussinesq model and pressure inlet and outlet boundary conditions are used. Results show that the most effective geometry is the one with baffles that drive flow in radial channels in addition to axial channels. Streamlines near the holes in papers show that that height of holes is too small to affect heat transfer and, so, the comparison between geometries with and without paper shows the types without paper have higher heat transfer coefficients.
S. Salari et al., "Heat Transfer Study in Oil Channels of a Power Transformer Winding ONAN Cooling System with and without Insulating Paper Based on Numerical Modeling", Applied Mechanics and Materials, Vol. 232, pp. 757-764, 2012