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HEAT TRANSFER


GHT engineers can offer expert advice on how to operate thermal fluids at the optimal temperature and implement proactive maintenance


strategies to improve sustainability


temperature of the fluid to the temperature outlined by the application requirements, rather than running the system at the maximum temperature specified for the fluid. Maintaining a lower temperature when feasible conserves energy, mitigates thermal degradation and improves system reliability. Running the system at the lowest temperature possible to achieve high-quality products can improve the energy efficiency of


TAKE A GRADUAL APPROACH TO IMPROVE EFFICIENCY


Here, Ian Silvester, lead project engineer at Global Heat Transfer, explains how manufacturers can maintain good thermal fluid system efficiency, without turning up the heat


common response to problems with a heat transfer system is to crank up the heat. However, the Arrhenius equation suggests that increasing temperature by just ten degrees can halve the expected lifespan of a fluid. Taking this step therefore increases costs, energy use and waste.


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Monitoring the condition of HTFs used for indirect heat transfer applications, such as food or pharmaceutical processing, can be difficult as the fluid is not visible once it enters the system. So without proper proactive maintenance, engineers won’t know there’s a problem until it impacts production — food products cook inconsistently, for example, or ingredients won’t blend and product quality drops. While it may be true that, in these scenarios, the quickest way to return to productivity is to crank up the heat, this won’t solve the underlying problem, and in many cases, will exacerbate the situation. Manufacturers initially match the fluid's operating temperature range to the application. However, they might be tempted to increase the heat if the fluid can withstand higher temperatures in order to maintain productivity. Thermal fluids are designed to offer reliable performance and longevity, but running the fluid at excessively high temperatures for prolonged periods can speed up the degradation process, as the Arrhenius equation explains. As the fluid breaks down, chemical reactions will form volatile compounds and by-products, such as heavy ends (including carbon), that contaminate the system. Carbon and varnish, for example, can block strainers, leading to cavitation, potentially


reducing the lifespan of the pump. They can also act as an insulator, preventing thermal fluid from taking heat away from the coil inside the heater case.


The presence of these contaminants will also reduce heat transfer efficiency, which will negatively impact product quality, alerting engineers to an issue — at which point the engineer might turn up the heat again. Choosing to further increase the system temperature to well above the needs of the application means that manufacturers will need to replace fluids more frequently, increasing operational costs and resource consumption.


Turning up the temperature can have negative repercussions on the facility environment, including increased energy consumption, increasing operational costs as well as the release of pollutants to the atmosphere.


Over time, excessive fluid degradation can compromise the efficiency of the system, putting pressure on core components that may degrade at a faster rate. The breakdown of the system results in more frequent replacements of fluid and system components, further contributing to waste generation. The degradation process can also result in the release of harmful emissions. To mitigate the environmental impact of a heat transfer system that runs at too high a temperature, thermal fluid experts can help determine if there is an alternative thermal fluid that better meets the needs of the application rather than what’s currently used in the system.


Engineers can maximise a thermal fluid’s lifespan by matching the operating


16 JULY/AUGUST 2024 | PROCESS & CONTROL


the facility. Additionally, thermal fluid and heat transfer equipment will operate more efficiently for longer periods at lower temperatures, reducing the frequency of maintenance, repairs and fluid replacement. If manufacturers have been operating the system at excessively high temperatures, or turned up the heat to boost productivity, significantly lowering the temperature is not the solution. Drastic temperature changes could disrupt chemical reactions that occur in heat transfer processes, which will negatively affect production and product quality. Instead, manufacturers can reduce the system temperature in increments. A careful assessment of the needs of the system and application enables engineers to mitigate potential risks associated with temperature changes, such as viscosity, heat transfer efficiency and product quality, which may initially cause reluctance to change. This incremental approach, as well as consideration of the benefits of temperature control, enables engineers to find a balance between product quality and system efficiency.


Making gradual and managed temperature adjustments is best for the system—reducing temperature in 5˚C increments, for example, will prolong the life of the fluid and reduce energy costs. Looking back to the Arrhenius equation, decreasing the temperature by just ten degrees can double the lifespan of a fluid. By considering the temperature of the fluid returning to the heater and the temperature that production equipment requires, engineers can implement a gradual approach. Then, engineers can continuously monitor system parameters and make adjustments to minimise impact on product quality. Engineers can continue reducing the temperature in increments until the system is at the right temperature to meet quality requirements in the most energy efficient way.


Global Heat Transfer www.globalhtf.com


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