How to test high-temperature heat transfer oil

I think the main ones are as follows:； 1. The acid value reaching 0.5 is measured in accordance with GB264－77. 2. The viscosity reaching 15% is measured in accordance with GB265－75. 3. A change in flash point of more than 20% is measured in accordance with GB267－77. 4. The residual carbon content (w%) reaching 1.5 is measured in accordance with GB268－77. Sampling and analysis of thermal conductivity should be carried out regularly, generally not exceeding once a year. :)

The following information provided by the original poster comes from website searches; personally, I think the physical properties are sufficient – the key aspects being heat conductivity, stability, and safety. This is for reference only. Physical properties of heat transfer oils: A range of physical properties of heat transfer oils, such as viscosity, vapor pressure, boiling range, initial boiling point, and flow point, are related to the performance of these oils. Viscosity is directly related to heat transfer efficiency; the lower the viscosity of the oil, the faster it can flow, and thus the higher the heat transfer efficiency. A liquid compound has a certain boiling point under a given atmosphere. Typically, heat transfer oil is a mixture, and the boiling points of its various components are not identical. The range between the lowest and highest boiling points among these oil components is referred to as the boiling range. The higher the boiling range, the higher the maximum operating temperature of the oil. Whether an oil is prone to catching fire can be determined by its vapor pressure, flash point, ignition point, and auto-ignition temperature. If oil evaporates easily into gas, it is prone to catching fire. The flash point, ignition point, autoignition point are also related to the volatility of oil. The amount of oil vaporization can be expressed by the oil’s vapor pressure. As the temperature rises, the amount of oil that vaporizes increases, and the vapor pressure rises accordingly. A given oil has a constant vapor pressure at a certain temperature. The flash point is the lowest temperature at which a mixture of oil vapor and air emits a brief flash of flame when brought near a flame. When the temperature of a certain oil rises to a specific level and ignition occurs, resulting in a flame that will not go out, the lowest temperature at which this phenomenon occurs is known as the ignition point. When the oil temperature rises to a certain level, it can catch fire spontaneously upon contact with air without the need for an ignition source. The lowest oil temperature at which spontaneous combustion occurs is known as the autoignition point. If the oil has a low vapor pressure, its flash point, ignition point, and autoignition point are high; in such cases, the oil is less likely to cause fires. Typically, the operating temperature of oil is above its flash point, which requires that the oil not come into direct contact with open flames or sparks; however, this operating temperature must be below the oil’s auto-ignition point. The safety of oil is also related to its operating temperature and its initial boiling point. Under certain conditions, the distillation temperature at the moment the first drop of distillate emerges from the end of the condenser is called the initial boiling point; this is related to the low-boiling-point fractions in the oil. For both safety and operating temperature considerations, a high initial boiling point is desired. The so-called flow point refers to the lowest oil temperature at which the oil can flow. Oil with a low flow point remains fluid even in the severe cold of the north; otherwise, it will make it difficult to start the oil furnace. What is the relationship between the physical properties of oil and its molecular structure? The physical properties of many oils are directly related to the intermolecular forces; if these forces are weak, the liquid evaporates easily, resulting in a high vapor pressure as well as lower boiling points and initial distillation points. Conversely, when the intermolecular forces decrease due to reduced attraction, the viscosity of the oil also decreases, and the boiling point drops accordingly. Where does intermolecular attraction come from? Why is there a difference in size? Ultimately, this force is an electrostatic attraction; there is a force between the positive end of one molecule and the negative end of another molecule, and the greater the charge on these positive and negative ends, the stronger the attraction. Intermolecular forces can be classified into the following types: (1) Forces between ions. (2) Dipole-dipole attraction. (3) Hydrogen bonds. (4) Van der Waals forces: In alkanes, the boiling point increases by approximately 20–30°C for each additional carbon atom. Therefore, among hydrocarbon-based heat transfer oils of the same type, as the molecular weight increases, the intermolecular forces become stronger; as a result, the vapor pressure of the oil decreases while its flash point and boiling point increase, which is beneficial for the performance of the heat transfer oil. However, the viscosity and flow point of oil increase as molecular attraction increases, which is detrimental to the performance of heat transfer oils. Therefore, we cannot choose a base oil that has low vapor pressure, high boiling point and flash point, while at the same time having low viscosity and pour point; when selecting a base oil, we must find a balance among these physical properties. The strength of van der Waals forces depends not only on the size of the molecules but also on their shape.

"We want to purchase Type 350 heat transfer oil. Do you mean heat transfer oil with a temperature of 350 degrees, or Type 350 according to domestic standards? For heat transfer oil at 350 degrees, the common types available on the market include DBT, MARLOTHERM SH, RP, T 66, etc., all of which are imported in their original form ； T 66 is hydrogenated triphenyl, DBT and MARLOTHERM SH are dibenzylmethyl toluene, RP is diarylalkane ； In actual use, the performance of T 66 is comparable to that of DBT and MARLOTHERM SH; RP seems to be less satisfactory, as Daosheng Company itself does not use RP in its own chemical production lines. If you are looking for a model of type 350 that meets domestic standards, then it depends on the temperature required by your production line. If the temperature remains around 300 degrees, it is more cost-effective to use synthetic oil; if you use domestically produced heat transfer oils, the costs will be high. The simplest way to determine the quality of oil is to take equal amounts of oil samples and heat them simultaneously, then observe which sample shows changes first – such as changes in the oil’s color, the formation of smoke or fumes, or the creation of carbon deposits. The oil whose changes occur later has better performance. Discussion QQ: 525224195

My company has also purchased two heat transfer oil heaters with a capacity of 2.5 million kcal; we need heat transfer oil of type 350. Domestic products are more affordable. Those who are familiar with this area could recommend some good brands as well as points to keep in mind when making the purchase. Thank you

The quality of thermal oil and the service provided by Shanghai Jiuxing Chemical are good