Heating Transfer Fluids’ Selection
A number of important properties which must be considered accurately for selecting a suitable heating-transfer fluid in a process are viscosity, heat exchange capacity, thermal conductivity coefficient, possible hazardous effects on humans, environmental damage and thermal degradation resistance. While oil-based fluids show high thermal resistance compared to water, glycols, and water-glycol mixtures; water-based fluids are still more popular in various industries due to providing lower viscosity and higher thermal conductivity.
Types of Heat Transfer Fluids
Normally, heating transfer fluids which are water-based types, are widely used in applications with temperatures lower than 250 Fahrenheit degrees such as medical or HVAC (heating, ventilation, and air conditioning). In low temperatures (up to 200 Fahrenheit degrees), the most suitable heat transfer fluids are brines or water, due to having high conductivity, low viscosity, and relatively low cost; Additionally, water and brines are mostly used in coolant processes, and glycols are the preferred choice in antifreeze applications. Water itself has the highest thermal conductivity among liquids due to its distinct specific heat.
As glycols can be mixed with water easily, glycols are preferred to be used as heat transfer fluids compared to oil-based fluids. To name a few of the most popular glycols in antifreeze applications, MEG and Propylene glycol can be named. On the other hand, oil-based fluids such as mineral or synthetic oils can be utilized in higher temperatures in the range of 300 to 750 Fahrenheit degrees.
TEG as another member of the glycols, has distinguished heating transfer capability which is ideal for many purposes, and can be satisfied neither by other types of glycols nor by water. TEG can be widely used in applications that are in the temperature range of 200 to 400 Fahrenheit degrees. In other words, it can perfectly fill the gap in the performance of oil-based and water-based heat transfer fluids, which makes TEG a distinct product globally.
Chemistry
TEG molecules consist of three linked MEG molecules, and subsequently, the thermal resistance of molecule against degradation is higher due to TEG’s huge structure and its long chains. As a result, the degradation rate of TEG is highly lower than other types of glycols such as MEG. Although, there is an issue regarding the mentioned, too. The bigger the molecule is, the higher the viscosity gets; Therefore, the pumpability of TEG in pipes and chemical reactors is lower than MEG.
Thermal Stability of TEG
While most water-based heat transfer fluids such as Monoethylene glycol and propylene glycols are only effective in temperatures below 250 to 300 Fahrenheit degrees, TEG can be utilized as a heat transfer fluid up to 390 Fahrenheit degrees without experiencing degradation. TEG which is used in such high-temperature ranges should be checked and tested periodically to make sure its capability is still intact. Moreover, periodical treatments for corrosion inhibition and pH maintenance are highly recommended.
TEG as Anti-freeze Protection
In cold environments, there is a huge requirement for chemical products that are capable of reducing the probability of water freezing. If fluid freezing is not controlled, catastrophic issues such as pipeline plugging or plant shutdown may happen. To address and prevent such issues, efficient heat transfer fluids have been utilized. One of the most distinguished fluids is TEG. Having perfect anti-freezing and heat transfer characteristics, TEG can be used in low-temperature areas (up to below 32 Fahrenheit degrees) for lowering freezing points of fluids. In addition, its lower viscosity compared to oil-based fluids, makes it a suitable candidate to minimize energy-requirement for pumping through pipes, energy conversion, heating systems, heat sinks, and other types of machines.
TEG as Natural Gas Dehumidifying
One of the most important applications of TEG is in dehumidifying natural gas. TEG is used widely to reduce water contents in natural gas which is flowed in the pipelines in order to minimize the possibility of pipeline plugging and water-related corrosions. Providing high heating-transfer properties, TEG can be used in different environments ranging from sub-zero to 390 Fahrenheit degrees. Moreover, other properties of TEG’s include low viscosity and less energy requirement for pumping are its advantages in the gas industry- compared to oil-based fluids.
Conclusions
TEG is highly efficient for high-temperature applications such as heat transfer in geothermal plants, heat exchanging in power generation plants, or petrochemical reactors regarding its high heat transfer coefficient.
In high-temperature conditions, TEG is a superior product compared to the most of other types of glycols due to its higher heat transfer capabilities.
TEG is a perfect candidate for replacing oil-based heat transfer fluids in applications with temperatures lower than 390 Fahrenheit degrees in order to minimize heat loss.
Having perfect anti-freeze and heat transfer characteristics, TEG can be used in low-temperature areas for lowering freezing points of fluids.
TEG is seldom used in custom cooling processes or household applications due to its high viscosity compared to water, brines, MEG, and Propylene Glycol.