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Specialist Materials for Industry and Science

Thermal Properties of MIDEL 7131

Thermal Properties of MIDEL 7131

The links below contain details of all the key thermal parameters for MIDEL 7131 fluid at the temperature ranges relevant to the majority of transformers.

These values are also represented graphically down to 0°C. They have either been measured over the whole temperature range by external laboratories, or calculated (interpolated or extrapolated) from the data.

Kinematic Viscosity


Specific Heat

Thermal Conductivity

Thermal Expansion Coefficient

Benefits of using MIDEL 7131

The above data will show that MIDEL 7131 can work as an effective coolant over a wide range of temperatures relevant to the majority of transformers.

Aside from the consistent high performance of MIDEL 7131, further benefits include its 100% fire safety record, durability and improved moisture tolerance. It also offers greater environmental protection than mineral oil alternatives, as well as providing a low maintenance option.

MIDEL 7131-filled transformers are also easier to clean and maintain than other options such as cast resin transformers. DGA testing can uncover potential faults early, allowing them to be repaired before the damage becomes too severe.

These properties have helped Midel fluids develop a reputation as a 'fill and forget' transformer oil, as they require much less work than competing products.


MIDEL eN is a natural ester, with thermal properties that allow it to perform at a level comparable to that provided by MIDEL 7131.

It is made using renewable materials and is readily biodegradable, offering an environmentally friendly option for use in sealed transformers.

If you would like to find out more about MIDEL 7131 or MIDEL eN, visit our documents or contact us for further information.

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Products of M&I Materials Ltd.