How many methods you ever know for thermal conductivity test standard ?
At present, there is no unified thermal conductivity test standard in the market. Due to the different test methods under different standards, the measured thermal conductivity of the material varies greatly. Then, to choose the appropriate test method, you must first understand the test standards for thermal conductivity.
Common international general standards are ASTM D5470, ASTM E1461 and ASTM E1530 ,those three standards are of the American Society for Testing and Materials (ASTM).
This standard is a test method for the thermal transmission characteristics of thermally conductive electrical insulating materials, using the steady-state heat flow method.
Principle: A certain amount of heat flow, pressure, test sample thickness and temperature difference between the hot plate / cold plate are applied to the sample to obtain the thermal conductivity of the sample. The sample needs to be a larger block in order to obtain a sufficient temperature difference.
This standard is a test method for determining the solid thermal diffusivity by the flash method (laser flash method). The high-intensity energy pulse irradiates the small and thin sample for a short time. The pulse energy is absorbed by the front surface of the sample and the temperature rise of the rear surface caused by it is recorded (temperature self-recording curve). The value of the thermal diffusion coefficient is calculated from the thickness of the sample and the time required for the temperature rise of the rear surface to reach a certain ratio.
Principle: A laser beam hits the upper surface of the sample, and the infrared detector is used to measure the temperature change of the lower surface. The actual measured data is the thermal diffusivity of the sample. It is also necessary to know the specific heat and density of the sample in order to obtain thermal conductivity through calculation. coefficient.
This standard is a test method for evaluating the heat transmission resistance of materials using a heat-protecting heat flow meter technology.
The test principle is almost the same as the ordinary heat flow method thermal conductivity instrument, the difference is that: around the measurement area (hot plate + sample + cold plate), a protective heater is added, heated to the average temperature of the sample, by reducing the sample and the surrounding The temperature difference between them can reduce the lateral heat loss and improve the measurement accuracy.
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