Regarding the issue of installing thermal resistors inside sleeves
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Regarding the installation of thermal resistors, ceramic and stainless steel protective sleeves are currently in use, with heat transfer oil filled inside these sleeves. When installing the thermal resistors, it is important to determine whether they touch the bottom of the sleeve; also, it is necessary to know if there is any difference in temperature when heating or cooling, and what that difference is. Additionally, it is important to figure out the optimal location within the sleeve from which the temperature of the material inside the tank can be measured most accurately
I just conducted an experiment: using a test tube filled with heat transfer oil and two thermistors of the same specification, the temperature difference between them at room temperature was 0.2 degrees. As the temperature in the laboratory flask increased to 100 degrees, the thermistor suspended in the hot oil (3 centimeters above the bottom) showed a faster increase in temperature; when the water temperature reached 70 degrees, the temperature difference between the two thermistors was nearly 5 degrees
This post was last edited by 1111111 on 2018-9-15 at 11:38. Hehe, the temperature is 70°C, and the readings from the two thermistors differ by almost 5°C – there’s nothing strange about that. After all, thermistors aren’t actual measuring elements used for calibration through heating; they’re simply standardized components, just like screws. Whether their consistency and accuracy are good or not depends entirely on luck. . . For example, I bought a pack of M3 nuts at an electronics market this spring. After using them a few times, I realized that out of those 100 nuts, maybe 10 to 20 of them wouldn’t fit into the screws at all. It was really frustrating; it took a ton of effort and caused a lot of hassle. Secondly, it is estimated that most of the thermal resistors available on the market today were produced by those who work in pig farming in Anhui and Jiangsu provinces; they do this as a side job after finishing their main work. These people are simply trying to earn some money through manual labor, and they certainly wouldn’t go through the process of conducting performance tests on the temperature sensing elements before using them in product manufacturing.
Regarding the temperature field, for a spherical or cylindrical temperature field, the position at 1/3 of the radius from the boundary is where the typical values of the temperature distribution are found; therefore, choosing this location as the point for temperature measurement is an ideal choice.
Indeed, the installation location has a significant impact on temperature measurement, far exceeding the errors inherent in the thermal resistor itself; I encountered a similar situation while conducting tests on resin temperature
Can something like thermal paste be added inside the sleeve?
The experiment he conducted involved one setup with heat transfer oil and another without it; it was actually a matter of the heat transfer rate, which can also be referred to as the response time. Heat transfer through air, in the absence of heat transfer oil, is very slow, with a significant delay
Thermal paste can also be used for horizontal installation, while thermal oil is sufficient for vertical installation. How expensive is thermal paste?