Effects of Nanoparticles Materials on Heat Transfer in Electro-Insulating Liquids

Grzegorz Dombek,Zbigniew Nadolny,Agnieszka Marcinkowska

doi:10.3390/app8122538

Grzegorz Dombek, Zbigniew Nadolny + Show 1 more

Open Access

https://doi.org/10.3390/app8122538

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Journal: Applied Sciences	Publication Date: Dec 7, 2018
Citations: 24	License type: CC BY 4.0

Affiliation: Poznań University of Technology

Abstract

This paper discusses the effect of doping of electro-insulating liquids with nanoparticle materials on the thermal properties of the obtained nanoliquids and heat transport in the transformer. Mineral oil, synthetic ester, and natural ester were used as base liquids. The effectiveness of doping base liquids with nanoparticles was supported by ultraviolet-visible (UV/VIS) measurements. In turn, Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) confirmed the absence of intermolecular interactions (i.e., hydrogen bonding). The influence of modification of electro-insulating liquids with fullerene C60 and titanium dioxide TiO2 nanoparticles on such thermal properties as thermal conductivity, specific heat, kinematic viscosity, density, and thermal expansion was investigated. Based on these properties and the theory of similarity, the cooling efficiency of the transformer filled with the analyzed nanofluids was determined. Nanofluids’ cooling effectiveness was compared with the cooling effectiveness of the base liquids. This comparison was supported by an analysis of Grashof, Prandtl, and Nusselt numbers. It has been shown that the modification of electro-insulating liquids with nanoparticles widely used in order to improve their dielectric properties, such as C60 and TiO2, does not have a significant influence on their thermal properties. The addition of fullerene C60 caused an increase in kinematic viscosity, which was compensated by the increase in specific heat. In the case of TiO2, the addition of this nanoparticle resulted in an increase in kinematic viscosity and a decrease in specific heat, which were balanced out by the increase in thermal conductivity. In summary, the heat exchange-capacity of liquids did not change due to doping with nanoparticles.

Highlights

Ensuring proper electrical insulation and heat dissipation out of devices are the main tasks for electro-insulating liquids which are used in electrical power equipment [1,2]
The heat generated by the core and the winding through the liquid is transferred to the ladle, from where it goes to the surroundings
The base liquids used for the research were Nytro Draco mineral oil (MO)

Summary

Introduction

Ensuring proper electrical insulation and heat dissipation out of devices are the main tasks for electro-insulating liquids which are used in electrical power equipment [1,2]. In the case of transformers, heat transport takes place along the heat source (core, windings), insulation system (paper impregnated with electro-insulating liquid and electro-insulating liquid), tank, and air. The fact that the electro-insulating liquid has the largest volume in the transformer cooling system makes it essential in heat transport. The electro-insulating liquid that flows through the oil channels cools the windings and core, taking away the heat from them. The heat generated by the core and the winding through the liquid is transferred to the ladle, from where it goes to the surroundings.

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