Pressureless heat transfer

Many industrial manufacturing processes use large amounts of thermal energy – be it for drying wood, heating chemical substances or paper smoothening. This so-called “process heat” is required at different, process-specific temperature levels.

In the temperature range of up to 430 °C, thermal oil has established itself in industry as a heat transfer medium for process heat in addition to steam. Thermal oil allows almost pressureless heat transfer up to 350°C, and comparatively low pressure up to 430°C. As it stays liquid even at those high temperatures it offers excellent controllability compared to steam.

In this article, learn about the advantages of thermal oil as a heat transfer medium and how you can increase the sustainability of industrial processes with thermal oil systems.

What is thermal oil and what are its benefits?

Thermal oil is usually a mineral, silicone-based or synthetic oil used in industry to cool and heat industrial systems and processes. In the context of industrial process heat, the thermal oil takes on the task of transporting thermal energy at the desired temperature level from the producer to the consumer. Further interesting background information on process heat can be found here.

Due to its thermal oil properties, heat transfer oil has become established as an alternative to steam in industrial process heat generation in the temperature range up to 430 °C. The advantageous thermal oil properties include, in particular, the high boiling point, which, in combination with a low freezing point, enables use in wide temperature ranges without the formation of steam.

The advantages of thermal oil at a glance:

• Virtually pressureless heat transfer over a wide temperature range
• Low maintenance of thermal oil systems
• No water treatment required
• Controllability
• Low capital expenditure

Heat transfer media in industry

In industrial process technology, heat is required at different temperature levels. Depending on the temperature level, different heat transfer media are suitable for transferring the thermal energy. In addition to thermal oil, the following media are also common industrial heat transfer media:

• Water: Water – whether in its liquid or vapor state – is an excellent heat transfer medium thanks to its high specific heat capacity. Especially steam offers the advantage of low-loss energy transfer through pipes.
• Air: Air can also serve as a medium for heat transfer, usually in open circuits. However, the specific heat capacity is much lower than that of water.
• Salt melts: Salt melts are usually mixtures of sodium nitrate and potassium nitrate. Temperatures of up to 550 °C can be realized.
• Liquid metals: Liquefied metals are used in special applications such as nuclear reactors as heat transfer media for extremely high temperatures.

Thermal oil or steam – which heat transfer medium is more suitable?

In industrial process heat transfer, the question often arises in the temperature range up to 430 °C as to whether thermal oil or steam should be used as the heat transfer medium. The main difference between the two media lies in the pressure level: While a very high pressure level is required for heat transfer with steam, thermal oil provides the process heat at much lower pressure. Below 355°C, systems only the pressure generated by the circulation pump must be considered.

The advantage: Thanks to the thermal oil properties, the design of the system technology is significantly easier and more cost-effective than with steam.

Using process heat sustainably – with thermal oil systems

The advantages of a thermal oil systems for the provision of process heat are manifold: In contrast to a steam boiler, the use of thermal oil does not require any water treatment which means that the investment costs are lower. In addition, corrosion does not occur in a thermal oil system, which also keeps maintenance costs low.

Thermal oil as a heat exchanger also has advantages in terms of sustainability, as it offers a long service life. Indirect heating by means of a thermal oil system also offers the advantage that several heat consumers can be supplied with one heater.

The thermal oil disposal in the industry

When disposing of thermal oil in industry, the requirements of the Waste Oil Ordinance (AltölV) must be observed. Depending on their type and composition, insulating and heat transfer oils may contain harmful substances. These include, for example, organic chlorine compounds, which occur in small proportions in addition to hydrocarbons. In addition, small amounts of heavy metals can also be found in some cases. The respective waste code must therefore be considered with regard to proper disposal.

If you have any questions about the use and disposal of thermal oil in industrial processes, please feel free to contact us. As an experienced developer and manufacturer of thermal oil equipment, AURA has extensive expertise in handling thermal oil in industrial processes.