Heat transfer fluids are critical for both circulation heaters and for industrial heating processes to function effectively. While a wide variety of other processes require the use of heat transfer fluids, no single type of fluid is an ideal fit for evert industry. Instead, there are several factors firms must look to when determining what the correct heat transfer fluid is for their specific sector and the processes involved.
In this blog, we’ll take an in-depth look at heat transfer oils examining the different types available and the factors to consider when selecting for your specific industry.
What are the different types of heat transfer fluids available?
Water is by far the most affordable heat transfer fluid available to use. As you would expect, it is almost always employed when it is an applicable option for an operation. However, water does come with a specific set of limitations that can make it an ineffective option for many industries. For example, its operable temperature range is typically low. Boiling occurs at 100°C and freezing at 0°C. As a result, industries involving high-temperature operations are unable to use water as a heat transfer fluid, and any operation where low temperatures are present will require other heating solutions or the use of specific additives.
In comparison to water, oils can offer a much wider utility range when acting as a heat transfer fluid. It is worth noting, however, that natural mineral oils will still experience a limited temperature range. For industries involving applications that exceed an operating temperature of 175°C the best solution is use a synthetic organic oil instead.
Synthetic organic oils can deliver improved thermal stability, along with providing a much greater operating temperature range. A wide variety of different heat transfer fluid types within this category can provide minimum temperatures as low as -80°C and maximum temperatures of around -400°C.
While their minimum temperatures are much lower than water, synthetic heat transfer oils are more often employed in industries involving processes with a temperature range of between 175°C and 400°C,rather than below 0°C. Operating conditions with lower temperatures are more likely to use inhibited glycol-based heat transfer fluids.
Inhibited glycol-based fluids are solutions made from inhibiting glycols and water. This type of heat transfer fluid is most employed for operations involving temperatures below 175°C However, they can perform at temperatures as low as -50°C.
These solutions can be either propylene glycol or ethylene glycol fluids depending on the application. For example, where there is potential contact with a supply of drinking water, using ethylene glycol-based heat transfer fluids is ideal as they have low oral toxicity.
Finally, molten salts can be used as heat transfer fluids for industries that feature high-temperature operations. This option is suited for temperature ranges between 285°C and 565°C. For temperatures exceeding 565°C, fluoride and chloride salts can instead be used as they provide greater stability. However, they are both more corrosive in nature than nitrate salts.
At temperatures as low as 285°C, when synthetic oils can be used, molten salt may be a better option as they present less risk of degradation at such temperatures and possess a lower vapour pressure.
Understanding selection factors for heat transfer fluids
Operations must be aware that there are four key factors that can influence what kind of heat transfer fluid will fit a specific industry, as well as the processes involved.
The first factor is temperature – the maximum and minimum operating temperatures always correlate directly to different fluid types. For instance, water has a much lower maximum temperature than any other type of heat transfer fluid, and molten salts can operate at substantially higher temperatures.
Another important consideration is pumpability. The heat transfer fluid must have the capacity to be pumped and then circulated at the required efficiency flow rate to maintain effective operations and heating.
In a similar respect, pressure requirements will also determine whether a heat transfer fluid is suitable for a specific industry. If the heat transfer fluid is suited better to pressures that are below or above the desired requirements of a process or project, it can result in inefficiency.
The last main factor to consider is thermal stability. If the heat transfer fluid will start to break down under the temperatures required in regular operation, it will alter the solution’s physical properties. This will not only impact operational efficiency but can also present a potential hazard and a serious damage risk to machinery.
Additional factors that may determine the best heat transfer fluid for an industry may include freezing, corrosion, hot and cold cycles, toxicity and long-term economy.
Selecting the correct heat transfer fluid for your industry is just as vital as picking the equipment itself. Always make an informed choice and refer to your original equipment manufacturer recommendations before picking a product.
