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Clive Jones explains how temperature can impact the performance and life span of a heat transfer fluid
Temperature plays a crucial role in everyday life. One small change could impact something simple such as a morning coffee or larger aspects such as seasons and personal health.
In manufacturing, temperature can mean the difference between productivity and costly mistakes, particularly when working with thermal oil.
In June 2019, Müller UK recalled two Cadbury desserts from supermarkets after discovering the possible presence of listeria monocytogenes. To kill off listeriosis in food, manufacturers must ensure products are heated to at least 74˚C. Just one- or two-degrees difference will compromise food products and could be dangerous to consumers, as Müller discovered.
Food manufacturing is not the only industry that demands precise temperature control.
Any industry that requires indirect heating processes should ensure that their system operates at the optimal temperature.
For example, an inaccurate temperature could prevent chemicals from blending in medications, stop a plastic from forming or could put the safety of workers on an offshore oil rig at risk.
Once products or facilities are compromised, manufacturers may have to throw away entire batches of products or evacuate and drain the heat transfer system, incurring high costs.
Arrhenius’ Law
Manufacturers can avoid operating at the wrong temperature by selecting the correct thermal fluid for an application. Heat transfer oils are designed to have a specific set of characteristics to ensure it is thermally stable and performs well at high temperatures.
Arrhenius’ law suggests that increasing temperature by just ten degrees can halve the expected lifespan of a fluid, so manufacturers should always look at operating temperature when selecting thermal oil.
Thermal fluid manufacturers will outline the entire operating temperature range of a fluid.
Engineers should select a fluid that can safely and efficiently reach the temperature required for the application.
Heating a thermal oil to higher temperatures than its specification will speed up degradation, as Arrhenius’ law suggests, decreasing thermal stability and productivity.
Efficiency
All heat transfer fluids degrade over time, but the speed of degradation will increase if the temperature exceeds the recommended range.
At high temperatures, the bonds that exist between hydrocarbon chains start to break, resulting in a process known as fouling, caused by the production of carbon in the system.
As the concentration of carbon increases, sludge starts to accumulate on the inside of heat transfer system pipework. This build up reduces the efficiency of the heat exchange.
As soon as this impacts the product, such as an inconsistently cooked food or chemical that does not blend, manufacturers need to cease production and drain, clean and flush the entire system.
Maintenance is key
Choosing the correct heat transfer fluid from the outset ensures that temperature will not impact production.
However, once the fluid enters the system, the correct fluid will still be operating at the high temperatures that will eventually lead to degradation.
Engineers should implement a preventative maintenance schedule, such as Global Heat Transfer’s Thermocare, to regularly sample heat transfer fluid and monitor the system.
Engineers should sample fluid when the system is hot, circulating and closed to get an accurate representation of fluid condition inside the system.
Results analysis can detect any issues, allowing engineers to plan maintenance so that it does not negatively impact production.
Whether a coffee is too hot or too cold should not make much of a difference to the rest of the day.
However, as Müller UK learnt, temperature can make much more of an impact in manufacturing. Carefully choosing a fluid based on its properties and implementing regular monitoring and maintenance is the only way to ensure that temperature does not negatively impact a production line.
Clive Jones is managing director of thermal fluid supplier Global Heat Transfer.
