Silicone Heat Transfer Fluid
Polydimethylsiloxane fluid as heat transfer media
PDMS fluid is a colorless and transparent liquid known for its excellent thermal conductivity. It is commonly used as a heat transfer medium in laboratory oil bath experiments, integrated heating and cooling machines, reaction kettles, and jacketed pots. As a heat transfer medium, silicone fluid circulates within heating devices, transferring heat to the object being heated, thereby achieving the desired heating effect.
Heat transfer media are generally divided into water and oil categories. Compared to water, oils offer a broader temperature range and are more stable, making them the preferred heat transfer media. Common oil-based heat transfer media include silicone oil and mineral oil. The table below lists the flash point data of common oils.
| Common Oils | PDMS Oil | Paraffin Oil | Mineral Oil | Transformer Oil | Diesel | Gasoline |
|---|---|---|---|---|---|---|
| Flash Point (°C) | 325 | 230 | 150 | 120 | 60 | 30 |
| Flammability | Non-flammable | Non-flammable | Non-flammable | Flammable | Flammable | Flammable |
As shown in the table, PDMS oil has the highest flash point. Compared to other non-flammable oils like mineral oil and paraffin oil, PDMS oil is colorless, odorless, non-toxic, and has excellent physiological inertness, chemical stability, and temperature resistance. Therefore, it is often used as a heat transfer medium.
When used as a heat transfer medium, PDMS oil is very stable below 180°C in air and can be used for extended periods. In air, its usage temperature ranges from 180 to 200°C. Above 200°C, it gradually oxidizes, with methyl groups oxidizing and cross-linking, increasing viscosity and eventually forming a gel. The graph below shows the viscosity changes of 100cSt PDMS oil when heated in air.
When reducing the contact area with air or using a closed system can increase the decomposition temperature of PDMS oil to 200°C. In vacuum or inert atmospheres, it can withstand temperatures up to 300°C.
During production, variations in manufacturing processes or cost control can lead to differences in product quality, such as unclear color and high volatile content, resulting in inadequate temperature resistance, significant smoke, and unpleasant odors in application. Our high-purity PDMS fluid can be used for extended periods below 180°C without these issues.
Polydimethylsiloxane fluid's cooling performance
In addition to excellent heat transfer performance, PDMS fluid also demonstrates good cooling performance, with numerous applications in freeze dryers and integrated heating and cooling machines. Freeze dryers freeze substances and heat them in a vacuum, converting water from solid to gaseous state. This process requires efficient heat transfer. PDMS fluid’s high thermal conductivity and stability make it an ideal heat exchange medium, effectively transferring heat from the source to the material in the freeze dryer, ensuring smooth processing. The pour point, indicating the lowest temperature at which the oil can flow, is crucial in assessing cooling performance. A lower pour point signifies better low-temperature performance. PDMS fluid’s pour point increases with viscosity, so low-viscosity silicone oils are typically chosen as cooling media.
Heat transfer fluid selection guide
When using silicone fluid as a heat transfer fluid, selecting the appropriate viscosity is crucial as it directly impacts heat transfer efficiency and system operation. The optimal viscosity depends on several factors, including:
- Operating Temperature Range: The viscosity of PDMS fluid varies significantly with temperature. It decreases at high temperatures and increases at low temperatures. Therefore, it’s essential to choose a PDMS fluid with a suitable viscosity based on the system’s operating temperature range to ensure good fluidity throughout the entire range.
- System Design: Factors like pipe diameter, pump power, and flow rate influence the flow of PDMS fluid. High viscosity can increase flow resistance and reduce heat transfer efficiency, while low viscosity may lead to leaks or pump malfunctions.
- Application Scenario: Different applications have varying viscosity requirements for PDMS fluid. For instance, indirect heating systems may necessitate higher viscosity silicone oil to minimize heat loss, whereas direct heating systems might require lower viscosity silicone oil to enhance heat transfer efficiency.
General Recommendations:
- Low-Temperature Applications (-50°C to 100°C): Typically, low-viscosity PDMS fluid, such as 10 cSt or lower, is preferred.
- Medium-Temperature Applications (100°C to 200°C): PDMS fluid with moderate viscosity, like 50 cSt to 100 cSt, can be chosen.
- High-Temperature Applications (Above 200°C): Higher viscosity PDMS fluid, such as 350 cSt or higher, is recommended. If temperatures above 200°C are required for extended periods, minimize the contact area between PDMS fluid and air, or conduct experiments in a closed system to enhance the thermal resistance of PDMS fluid. Alternatively, using phenyl silicone fluid, which introduces phenyl groups into the molecular chain of dimethyl silicone fluid, can significantly improve its thermal resistance.
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