After the heat transfer oil reaches a certain temperature, its flow rate begins to fluctuate. Why is this?
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This post was last edited by Zhang Liming on March 4, 2011, at 22:57. After the temperature of the heat transfer oil rises to a certain level, its flow rate begins to fluctuate. However, when the setpoint temperature at the outlet of the thermal oil furnace is lowered slightly, the fluctuations cease. Why is this so? When a heat transfer fluid is exposed to high temperatures for a long time, the interatomic and intermolecular bonds break down, causing the compound to decompose. The decomposition products mainly include gases, low-molecular-weight substances, and free radical molecules. This free radical molecule polymerizes with other molecules, forming active groups of polymers. The polymerization reaction that occurs is chain-like; even at a certain temperature, over time both the molecular weight and the amount of polymer produced tend to increase. Indicators such as viscosity undergo slow changes. This subject could be the real cause.
Low liquid level in the buffer tank, high circulating volume of thermal oil, low initial boiling point of thermal oil, etc
The operating pressure is low, and vaporization occurs.
To what temperature does it rise? It’s possible that there is a relatively large amount of moisture in the heat transfer oil; at high temperatures, this moisture vaporizes ； Or, when the temperature is too high, some of the heat transfer oil decomposes, producing gases.
Reply to 1# Zhang Liming: The temperature of the heat transfer oil reaches the bubble point temperature under the operating pressure of this medium, leading to vaporization; or issues related to the selection and placement of heat transfer oil pumps.
The temperature and pressure of a substance are interrelated; when the pressure remains constant and the temperature rises, the substance will vaporize； If the process requires high temperatures, it is recommended to replace the heat transfer oil.
On one hand, we’re trying to figure out the reasons behind issues with certain equipment; perhaps some equipment behaves erratically under these conditions. On another hand, in terms of the process, the temperature of the materials being heated by the thermal oil shouldn’t fluctuate greatly. Additionally, there’s also the issue related to the thermal oil itself, such as its dehydration
Heat transfer oil becomes unstable when used at temperatures above high temperatures (300). Gasification leads to operational instability.
Generally, the cause of such pressure fluctuations is that the low-boiling components in the heat transfer oil have not been removed.
I agree with chinazwr’s views; his analyses make a lot of sense. After ruling out any equipment issues, one possible cause is the slight vaporization of oil, while another is the presence of water in the heat transfer oil. In our facility, it’s quite common for water contamination in the heat transfer oil to cause fluctuations in flow rate.