Numerical study on nanofluids natural convection heat transfer inside power transformer windings

Yunpeng Zhang,Xinsheng Yang,Huihuan Wu,Hui Yang,Weinong Fu,Siu-Lau Ho,Yufei Jie

doi:10.1063/1.5130146

Abstract

As an innovative approach to improve the cooling efficiency of fluid, the use of nanofluids has attracted increasing attention in engineering applications. In this paper, the impact on the natural convective heat transfer in disc-type transformer windings due to transformer oil-based nanofluids is studied numerically. A low-voltage winding using nanofluid (SiC/oil) as the coolant is modelled two-dimensionally and simulated by computational fluid dynamics and the multi-phase mixture model. The numerical method is validated with the existing results of transformers using conventional oil cooling, and grid-independence study is carried out for the nanofluid flow. Compared with transformer oil cooling, the temperature of nanofluid cooled winding is significantly reduced, while the temperature trend along the flow direction remains essentially the same. Moreover, the effects of nanofluid on the mass flow rate and the coolant temperature have been taken into consideration in the heat transfer analysis.

Highlights

Oil-immersed power transformer is one of the most commonly used transformer types, especially for high-voltage and highpower applications
To accurately predict the temperature of windings, thermal-hydraulic networks2 and computational fluid dynamics (CFD) method3,4 are used to build the thermal model. Both windings and coolants are included in the thermal model, as there is a strong coupling between the heat transfer and the fluid flow, especially for oil cooling (ON) transformers
To evaluate the impact of nanofluid (SiC/oil) in transformers on their heat transfer performance, this paper develops a numerical model for the disc-type windings in natural nanofluid cooling transformers

Summary

INTRODUCTION

Oil-immersed power transformer is one of the most commonly used transformer types, especially for high-voltage and highpower applications. In oil forced cooling (OF) transformers, pumps are used to increase the velocities of flow to improve the heat transfer coefficients. To accurately predict the temperature of windings, thermal-hydraulic networks and computational fluid dynamics (CFD) method are used to build the thermal model. Both windings and coolants are included in the thermal model, as there is a strong coupling between the heat transfer and the fluid flow, especially for ON transformers. To evaluate the impact of nanofluid (SiC/oil) in transformers on their heat transfer performance, this paper develops a numerical model for the disc-type windings in natural nanofluid cooling transformers. Changes in mass flow rate and coolant temperature are considered in the analysis of nanofluid cooling

Geometry and boundary conditions

Material properties

The mixture model

RESULTS AND DISCUSSION

CONCLUSION