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Home > Heat Transfer Media > Frequently Answered Questions

Heat Transfer Media

Frequently Answered Questions

Q&A for Customers
FAQs on heat transfer fluids

How to select heat transfer fluids

Q1. We are thinking of introducing a heat transfer system. Could you tell us how to select a suitable heat transfer fluid?

A1. It is important to fully discuss with your heat medium manufacturer before making decision by taking into account the heat medium characteristics, such as physical property and thermal stability, and the service conditions, such as service temperature, equipment used and locational condition.

Q2. What are advantageous physical properties of heat medium to be considered in selecting heat transfer fluids?

A2. Typical advantageous physical properties are listed below:

Thermal conductivityHigher thermal conductivity is better.
Thermal energy (fluid density x heat capacity)Higher thermal energy is better.
ViscosityLower viscosity in the low temperature range gives advantage in selecting circulating pumps.
Flash pointHigher flash point involves lower risk of ignition.
Auto ignition temperatureHigher auto ignition temperature involves lower risk of self-ignition.
Explosion limitsNarrower explosion limits involves lower risk of explosion.
Pour pointHeat transfer fluid with lower pour point can more easily be handled. If heat transfer fluid with a high pour point is used, the piping must be provided with steam tracing.

Deterioration of heat transfer fluids

Q3. We would like to know how far the heat transfer fluid we use has been deteriorated.

A3. We provide heat medium deterioration analysis service at no charge. We recommend you to make use of the service. For more information, see "Recommendation of free heat transfer fluids analysis".

Q4. Could you tell us different types of deterioration of organic heat transfer fluids?

A4. Deterioration of heat transfer fluids can be roughly divided into three types: heat deterioration, oxidation degradation and deterioration caused by the inclusion of foreign substances.

What is the heat deterioration?
The heat deterioration refers to deterioration caused by heat. When an organic heat transfer fluid is exposed to a high temperature over a long period of time, the inter-atomic and inter-molecular bonds will be weakened to generate fragments. These fragments include gases, monomeric substances and radical molecules. The radical molecules are likely to join other molecules, which may cause polymerization reaction. These molecules will gradually change in color from yellow to dark brown and finally to black.
What is the oxidation degradation?
A heat transfer fluid has oxidation degradation when it is exposed to oxygen contained in the air. Oxidation produces organic acids, which accelerate the polymerization reaction of the heat transfer fluid. Remember that oxidation degradation develops faster than heat deterioration. As oxidation degradation develops, the fluid increases in viscosity and changes in appearance as in the same way as for heat deterioration. The organic acids generated through oxidation will corrode the equipment if water exists.
What is the deterioration caused by the inclusion of foreign substances?
A heat transfer fluid has this type of deterioration when a foreign substance such as heated material mixes in the fluid. Some foreign substances accelerate the chemical decomposition or polymerization of the fluid, which may lead to dramatic deterioration.

Q5. Could you tell us effective measures to prevent organic heat medium from deteriorating?

A5. Organic heat medium can be kept from deteriorating with the following measures:

Heat deterioration prevention
The biggest factor that may result in heat deterioration of organic heat medium is the surface temperature of the heat transfer walls, such as the heating surface of the boiler. It is necessary for you to fully discuss in advance with your heat medium manufacturer particularly when you use the heat medium at a temperature close to the maximum service temperature.
Oxidation degradation prevention
The heat transfer system should be designed so that the high temperature heat medium cannot be exposed to air. In a liquid medium circulation system, nitrogen gas seal equipment may be used in the expansion tank or the heat medium may be utilized as oil seal itself.
Prevention of the inclusion of foreign substances
The inclusion of foreign substances may be attributed to one or more of the causes listed below. These causes should be clearly identified and properly addressed.
・Heated materials that exist in the processing zone: Crack in the heat transfer surface of heat exchangers or jackets
・Water: Insufficient drying or co-washing of the heat transfer piping before charging of the heat medium. Insufficient nitrogen gas sealing of expansion tanks. Poor management of heat medium storage tanks and drums.
・Remaining oil: Incomplete removal of heavily deteriorated heat medium or insufficient cleaning during replacement.
・Heat medium containing too much low-boiling components: Heat medium that had been collected during venting or purging was directly put back into the fluid heating system.


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