Last Updated on November 16, 2024 by 35vwlynfv0rq

I. Introduction to heat transfer oil

(A) Definition and Applications of Heat Transfer Oil

Heat transfer oil, also known as thermal fluid, is a specialized type of liquid medium used for transferring heat from one location to another within a closed system. It plays a crucial role in numerous industrial applications where efficient heat transfer is essential. In industrial fields, it is widely utilized in various processes such as chemical manufacturing, food processing, oil refining, and textile production. For example, in chemical plants, it helps maintain the required temperatures for different chemical reactions. In food processing, it ensures the proper heating and cooling of products during different stages of production.

(B) Importance of Heat Transfer Oil in Energy Transmission

Efficient heat transfer is of great significance when it comes to heat transfer oil. It enables the smooth operation of industrial processes by ensuring that heat is accurately and promptly transferred to the desired locations. This not only improves the productivity of the overall process but also helps in conserving energy. By minimizing heat losses during the transfer process, it allows industries to operate more sustainably, reducing both energy costs and environmental impact.

II. Key Properties for Optimal Performance of Heat Transfer Oil

(A) Heat Transfer Efficiency

The efficiency of heat transfer is a vital property of heat transfer oil. It determines how effectively the oil can transfer heat from a heat source to the target area. The following table presents an analysis of factors affecting heat transfer efficiency, along with some typical quantitative technical indicators:

Factors	Detailed Description	Impact on Heat Transfer Efficiency Explanation	Typical Quantitative Indicators
Viscosity	Refers to the internal resistance of the oil when flowing. The higher the viscosity, the slower the oil flows.	Higher viscosity will impede heat transfer. Because it restricts the movement of the oil within the system, making it difficult for heat to be transferred quickly along with the flow of the oil, thus reducing the heat transfer rate.	Viscosity is usually measured in centipoise (cP). For common heat transfer oils, the viscosity at 20°C can range from 10 cP to 500 cP. A lower viscosity within this range generally indicates better flowability and potentially higher heat transfer efficiency.
Thermal Conductivity	Reflects the ability of the material to conduct heat.	The higher the thermal conductivity of the heat transfer oil, the easier and faster it can conduct heat, enabling more efficient transfer of heat from the heat source to the target area, thereby increasing the heat transfer efficiency.	Thermal conductivity is typically measured in watts per meter-kelvin (W/(m·K)). Good quality heat transfer oils usually have a thermal conductivity in the range of 0.1 to 0.2 W/(m·K). Higher values within this range are favorable for heat transfer.
Temperature Difference	The temperature difference between the heat source and the target area.	Generally, following the principle of heat conduction, the larger the temperature difference, the stronger the driving force for heat transfer, and the higher the heat transfer rate, which is more conducive to the rapid transfer of heat.	There is no fixed quantitative limit for temperature difference, but in industrial applications, a temperature difference of 50°C to 200°C is often encountered. Larger temperature differences within a reasonable range can significantly enhance heat transfer efficiency.

(B) Thermal Stability

Thermal stability refers to the ability of the heat transfer oil to withstand high temperatures without undergoing significant degradation or chemical changes. The measuring indicators of thermal stability include the rate of oxidation, formation of deposits, and changes in physical properties over time. To maintain thermal stability, certain conditions need to be met, such as proper temperature control within the operating range specified by the Manufacturer, regular monitoring of the oil’s condition, and avoiding exposure to contaminants that could accelerate degradation.

Typical quantitative technical indicators for thermal stability evaluation include:

• Oxidation rate: Measured in terms of the increase in acid value per unit time. For a well-performing heat transfer oil, the acid value increase should be less than 0.1 mg KOH/g per year under normal operating conditions.
• Deposit formation: Quantified by the amount of sediment that accumulates in the system over a certain period. For example, after continuous operation for 1000 hours at a specific temperature, the amount of deposits should be less than 0.5% of the initial volume of the heat transfer oil.

(C) Oxidation Resistance

The oxidation resistance mechanism of heat transfer oil involves the presence of antioxidants that prevent the oil from reacting with oxygen in the air. When the oil is exposed to air, especially at elevated temperatures, oxidation can occur, leading to the formation of sludge, acids, and other harmful byproducts. The impact of oxidation resistance on the lifespan of heat transfer oil is significant. A higher level of oxidation resistance can extend the useful life of the oil by reducing the rate of degradation, thereby saving costs associated with frequent oil replacements.

Quantitatively, the level of oxidation resistance can be evaluated by the following indicators:

• Antioxidant content: Usually measured in percentage by weight. A higher antioxidant content, such as above 0.5% by weight, generally indicates better oxidation resistance.
• Induction period: Measured by the time it takes for the oil to start significant oxidation under specific test conditions. For a good-quality heat transfer oil, the induction period should be at least 1000 hours under standard test conditions (e.g., at a certain temperature and in the presence of a certain amount of oxygen).

(D) Low-Temperature Fluidity

In low-temperature environments, the flow characteristics of heat transfer oil change. Some oils may become more viscous or even solidify, which can disrupt the heat transfer process. The measures to improve low-temperature fluidity include using oils with appropriate pour points (the lowest temperature at which the oil will flow), adding pour point depressants, and ensuring proper insulation of the system to prevent excessive cooling of the oil.

Quantitative indicators related to low-temperature fluidity include:

• Pour point: Measured in degrees Celsius. Different applications may require different pour points. For example, in some cold climate applications, heat transfer oils with pour points below -20°C may be preferred to ensure proper flowability even in extremely cold conditions.
• Viscosity at low temperatures: Similar to the measurement of viscosity at normal temperatures, but focused on the viscosity of the oil at low temperatures. For instance, at -10°C, the viscosity of a suitable heat transfer oil should not exceed 500 cP to maintain acceptable flowability for heat transfer operations.

(E) Compatibility with Equipment

Different equipment has specific requirements for heat transfer oil. For example, some pumps may require oils with certain viscosities to ensure proper lubrication and efficient operation. The methods for testing compatibility involve laboratory analyses to check for any adverse reactions between the oil and the materials used in the equipment, such as corrosion or degradation of seals. Compatibility is crucial to avoid equipment failures and ensure the long-term reliability of the heat transfer system.

Quantitative aspects of compatibility testing may include:

• Corrosion rate: Measured in terms of the amount of metal loss per unit area per unit time. For example, when testing the compatibility of heat transfer oil with a particular metal used in the equipment, the corrosion rate should be less than 0.01 mm/year under normal operating conditions.
• Seal degradation: Quantified by the change in physical properties (such as hardness, elasticity) of the seals after exposure to the heat transfer oil for a certain period. A negligible change in these properties indicates good compatibility with the seals.

III. Selection Strategies of Heat Transfer Oil Based on Key Properties

(A) Selection According to Specific Application Requirements

In various industrial scenarios, the emphasis on different properties of heat transfer oil varies. The following table illustrates this, along with relevant quantitative considerations:

Industrial Scenario	Emphasized Properties of Heat Transfer Oil	Reason Elaboration	Relevant Quantitative Considerations
Chemical Manufacturing	Thermal Stability, Compatibility with Equipment	In the process of chemical manufacturing, chemical reactions are often accompanied by high-temperature environments and the presence of corrosive substances. Heat transfer oil with good thermal stability can maintain its performance stability under such high-temperature conditions without significant degradation or chemical changes. And the compatibility with equipment can ensure that the heat transfer oil does not have adverse chemical reactions with the materials in the equipment, such as corroding the equipment or causing damage to seals, thus ensuring the normal operation of the equipment.	For thermal stability, the acid value increase should be less than 0.1 mg KOH/g per year and the deposit formation should be less than 0.5% of the initial volume after 1000 hours of continuous operation. For compatibility, the corrosion rate should be less than 0.01 mm/year and the seal degradation should be negligible.
Food Processing	Heat Transfer Efficiency, Low-Temperature Fluidity	For the food processing industry, precise temperature control is crucial for ensuring food quality. High heat transfer efficiency enables the heating and cooling processes in the production process to reach the required temperatures more accurately. At the same time, good low-temperature fluidity ensures that in the cooling stage of food processing, the heat transfer oil can still flow normally in a low-temperature environment, maintaining the stable operation of the entire heat transfer system and avoiding affecting the processing process due to the fluidity problem of the oil.	For heat transfer efficiency, the thermal conductivity should be in the range of 0.1 to 0.2 W/(m·K) and the viscosity at 20°C should be within a reasonable range (e.g., 10 cP to 500 cP). For low-temperature fluidity, the pour point should be below -20°C (in some cold climate applications) and the viscosity at -10°C should not exceed 500 cP.
Oil Refining	Oxidation Resistance, Heat Transfer Efficiency	The oil refining process is usually in an environment of high temperature and the oil is released to air. Heat transfer oil with strong oxidation resistance can effectively resist oxidation reactions, preventing the formation of harmful byproducts such as sludge and acids due to oxidation, and avoiding the decline of its own performance. High heat transfer efficiency helps to achieve rapid and efficient transfer of heat in each stage of oil refining, improving the overall efficiency of the oil refining process.	For oxidation resistance, the antioxidant content should be above 0.5% by weight and the induction period should be at least 1000 hours under standard test conditions. For heat transfer efficiency, the thermal conductivity should be in the range of 0.1 to 0.2 W/(m·K) and the viscosity at 20°C should be within a reasonable range (e.g., 10 cP to 500 cP).

(B) Comprehensive Consideration of the Balance of Each Property

When selecting heat transfer oil, it is essential to balance the relationship between different properties. For example, an oil with extremely high heat transfer efficiency but poor thermal stability may not be a suitable choice as it could degrade quickly under operating conditions, leading to reduced performance and potential equipment damage. Therefore, a comprehensive assessment of all key properties is necessary to ensure the optimal performance and longevity of the heat transfer system.

IV. Correct Usage and Maintenance of Heat Transfer Oil

(A) Precautions during the Usage Process

During the usage of heat transfer oil, several operating specifications and safety points need to be adhered to. Firstly, the temperature of the oil should be carefully monitored and kept within the recommended range to avoid overheating or undercooling, which could affect its performance and lifespan. Secondly, proper ventilation is required in the area where the oil is used to prevent the accumulation of any potentially harmful vapors. Additionally, any leaks should be taken care of promptly to avoid spills and potential safety hazards.

(B) Importance and Measures of Regular Maintenance

Regular maintenance of heat transfer oil is of utmost importance. The basis for determining the maintenance cycle depends on factors such as the operating conditions of the system, the type of heat transfer oil used, and the manufacturer’s recommendations. Common maintenance operations and inspection items include checking the oil’s viscosity, acidity, and appearance for any signs of degradation. Sampling and laboratory analysis of the oil may also be carried out periodically to assess its overall condition. Any necessary replacements or treatments should be implemented promptly to ensure the continued efficient operation of the heat transfer system.

For maintenance, the following quantitative guidelines can be considered:

• Viscosity change: If the viscosity of the heat transfer oil changes by more than 20% from its initial value, it may indicate a significant degradation and require further investigation or replacement.
• Acid value increase: If the acid value of the heat transfer oil increases by more than 0.2 mg KOH/g compared to its initial value, it is a sign of possible degradation and should be monitored closely or addressed with appropriate treatment.