Thermal oils should have a high heat transfer as the main property.
Water is the best medium for heat transfer, but has its limitations at colder and higher temperatures. That is why ultra-thin oils (chemicals) are used for this. These are still liquid far below freezing point and have a much higher boiling point than water.
The lower or higher the desired temperature is, the higher the bar should be properties to be laid for what the quality, read: chemical stability, should be.
The synthetic thermal oils are made up of different types of raw materials and compositions, which give each product its specific and unique properties.
There are 17 different Therminol® products available for a temperature range from -115ºC to + 400ºC.
In addition to excellent heat transfer, chemical stability should also be of concern wear for high durability of the thermal fluid.
The relative ratio of low boiling and high boiling formations and the solubility of the high boiling fractions can vary widely and are critical factors in evaluating fluid properties, predicting top-up costs and the overall risk of degradation products.