Detailed Explanation of ＂Thermal Conductivity＂

作者：admin 来源：未知发布时间：2019-01-07 18:04 浏览量：

Today we are going to popularize our knowledge about thermal conductivity. Before that, we should first understand the heat conduction.

Heat conduction is closely related to our daily life, such as:

导热系数原理,散热原理介绍,导热系数,AOK

These phenomena include a physical process of heat transfer, heat conduction (referred to as heat conduction), refers to the heat transfer process between two objects in contact with each other and at different temperatures, or between different parts of the same object without relative macro-displacement.

Thermal conductivity (also known as thermal conductivity) is a physical quantity indicating the thermal conductivity of materials, which reflects the thermal conductivity of materials.

The definition of thermal conductivity is: under steady heat transfer condition, the temperature difference between the two sides of a material 1 m thick is 1 degree (K, C), and within 1 second (1s), the heat transferred through the area of 1 square metre is in watt/meter degree (W/(m K), where K can be replaced by.

导热系数,导热原理,AOK

The thermal conductivity of the material is not only related to the material type, but also to its microstructure and filler content. In scientific experiments and engineering designs, the thermal conductivity of the materials used needs to be measured accurately by experimental methods. There are many methods to test thermal conductivity, such as steady-state hot plate method (reference standard: ASTM D5470), laser flash method (reference standard: ASTM E1461), Transient plane heat source method (reference standard: ISO 22007-2). The data obtained by different methods and test standards will be different. At present, ASTM D5470 and ISO 22007-2 are two common international testing standards in thermal conductive silicone film industry.

ASTM D5470 is a standard test method for thermal transmission characteristics of thermal conductive electrical insulating materials developed by American Material Testing Association. The thermal conductivity of the samples is obtained by applying a steady-state hot plate method to test the thickness of the samples and the temperature difference between the hot plate and the cold plate.

稳态热板法原理

稳态热板法原理（图）

博里业定律：

热阻：

导热系数：

This test method can better simulate the actual use state and reflect the thermal conductivity through thermal resistance. Aochuan Technology Co., Ltd. owns DRL-II, DRL-III thermal conductivity tester and LW-9389 interface material thermal resistance and thermal conductivity tester, which can be used to test thermal conductivity in accordance with ASTM D5470 standard.

DRL-II型导热系数测试仪

DRL-II型导热系数测试仪（图）

DRL-III 型导热系数测试仪

DRL-III型导热系数测试仪（图）

LW-9389型界面材料热阻及热传导系数仪

LW-9389型界面材料热阻及热传导系数仪（图）

Many famous thermal conductive silicone film manufacturers at home and abroad also adopt this test method and standard. However, this method requires a certain thickness sample to obtain sufficient temperature difference; contact thermal resistance will affect the test results; in order to achieve steady state, the test time is usually longer.

So is there a simple and fast way to measure the thermal conductivity?

Referring to international standard ISO 22007-2, Transient Planar Heat Source Method (TPS) is the most convenient and accurate method to study the thermal conductivity of materials at present. It usually takes only a few minutes to test once. It is a new technology that can simultaneously measure thermal conductivity, thermal diffusivity and heat capacity per unit volume when studying materials.

This method uses a Hot Disk probe, which we also call Hot Disk method. The Hot Disk probe is a conductive mode with a double helix structure and is etched with a thin metal sheet (such as nickel). The double helix structure is sandwiched by two thin insulating materials (polyimide, mica, etc.), similar to the sandwich structure.

Hot Disk Probe (Two Helix Probes as Heating/Sensing Elements) （图）

Its principle is based on the transient temperature response generated by a disc heat source stepped in infinite medium. A plane probe made of thermal resistive material nickel is used as heat source and temperature sensor. The relationship between the thermal resistance coefficient of nickel and temperature and resistance is linear. The heat loss can be known by understanding the change of resistance, thus reflecting the thermal conductivity of the sample.

The company has Hot Disk 2500S heat conductivity tester imported from Sweden, which can quickly and accurately measure the conductor coefficient for customers with reference to the international standard ISO 22007-2.

Hot disk 导热测试仪

Hot Disk Thermal conductivity tester

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