Smart science to improve lives™
Energy Technologies
  • Login | Register
Energy Technologies
Blue electric vehicle using dielectric fluids, driving on coastal road with sea at one side and forest at the other

Dielectric fluids

We create and make group V base oils for use in dielectric fluids. The fluids can impart performance and stability to dielectric fluid formulations containing PAO and Group III chemistries.

A dielectric fluid is an electrically non-conductive liquid that has a very high resistance to electrical breakdown, even at high voltages. Electrical components are often submerged or sprayed with the fluid to remove excess heat. The thermal conductivity and specific heat capacity of the liquid is higher than that of air, which makes the process more efficient at removing waste heat to cool high power electronics.

In electric vehicles, dielectric fluids are now being developed to cool the battery, electric-motor, power electronics and electric transmissions. The fluids must have high thermal conductivities and low viscosities to aid efficient heat transfer and pumping efficiency.

EV car battery pack Electric car lithium battery pack

What do we offer for dielectric fluids?

Our group V base oils for use in dielectric fluids are high-performance ester chemistries with excellent sustainability profiles. These fluids can impart performance and stability to dielectric fluid formulations containing PAO and Group III chemistries.

Our heritage in tribology also means we can continue to provide expert advice and speciality additives where friction reduction and anti-wear properties are important. These are increasingly important in electric and hybrid vehicles as the industry moves to low sulphur, lower viscosity formulations, which must have new material compatibility and operate under different conditions.

What are the most important properties of dielectric fluids?

There are several figures of merit that can be used to evaluate the heat transfer capabilities of fluids. One such number is the Mouromtseff number, which allows the heat transfer capability of different fluids to be compared. 

The Mouromtseff number, outlined below, indicates how efficiently a fluid can transfer heat, assuming the same hardware setup and fluid flow. (e.g. laminar or turbulent). 

Where notation is defined as: density (ρ), thermal conductivity (𝜆), specific heat capacity (Cp) and viscosity (v). The exponents a, b, d and e can be found from appropriate heat transfer correlations. The fluid with the higher Mouromtseff number has the better heat transfer properties when comparing two fluids.

The exponential factors of the Mouromtseff number are dependent on the flow characteristics. If they are constant, heat transfer can be maximised by increasing density, thermal conductivity, and heat capacity, whilst obtaining the lowest possible viscosity.

What types of fluid can be used as dielectric fluids? 

Traditionally, dielectric oils have been used to cool transformers, capacitors, high voltage cables and switchgear, providing electrical insulation and suppressing unwanted electrical discharge.

There is a great variety in the type of oil that can be used as the insulative fluid, and the chemistry, performance and sustainability of these oily fluids vary greatly. The table below summarises different dielectric fluids and their typical properties. 

Compatible base oils can be formulated into a single fluid, providing property benefits beyond that of a fluid formulated with a single chemistry.

What other attributes of dielectric fluids are important? 

Material compatibility and property degradation upon aging are also important attributes of dielectric fluids.

With the introduction of new polymers, operating conditions, and direct contact with metals in high voltage environments, many new tests are required to validate and approve electric vehicle fluids.

Whilst the industry has no standard test methods defined for these new conditions, you can speak to us about how our industry knowledge and testing programmes can help you define future dielectric fluid specifications. 

Why should you speak to us about dielectric fluids? 

Whether you are a formulator, additive company or original equipment manufacturer (OEM), we  can work with you to develop new and novel synthetic esters to help improve premium dielectric fluid formulations.

We are world-leading experts in the synthesis and manufacture of synthetic esters, having done so for over 70 years on a global scale, collaborating with our customers to create unique speciality chemistry.

Esters offer premium performance and sustainability and can offer best-in-class performance when used in dielectric fluid formulations.

Whitepaper: Properties of esters for use as dielectric fluids

941.7 KB
Close up of a technician with a gloved hand working on electric vehicle and battery cooling and thermal management

Read more about dielectric fluids in EV applications

Dielectric fluids can be applied in electric motors, battery systems and power electronics. They can improve the performance of electric vehicles, to improve safety and extend vehicle range.
Read more

Recommended products

Xenitron™  3221

Xenitron™ 3221

A dielectric base oil suitable for blending into PAO and mineral oil dielectric fluid formulations.

We can find a solution for your needs.