Thermal conductivity is an important performance of thermal insulation material, which is commonly expressed as thermal conductivity. Common thermal conductivity test standards include European standard EN12667, American standard ASTM C518, national standard GB / T10295, etc. In addition to thermal conductivity, we often hear the thermal resistance value. In fact, thermal conductivity and thermal resistance are two different concepts, but there is a certain relationship between them. Nanjing Smart focuses on the performance and fire testing of all kinds of building materials, and has rich experience in thermal conductivity testing. If necessary, you can call the hotline 025-86583475
Thermal conductivity (Thermal Conductivity) is the physical measure of the thermal conductivity of a substance in W / (m . K) or W / (m . ℃). It represents the heat transmitted by a material per unit thickness, unit area, per unit temperature difference. The larger the thermal conductivity is, the better the thermal conductivity of the material is.
Thermal resistance (Thermal Resistance) is a physical quantity that reflects the degree of obstruction to heat transfer in ℃ / W or K / W. It represents the ratio of the heat transmitted by a material per unit thickness or unit area per unit time to the heat passing through the material per unit time. The greater the thermal resistance is, the worse the thermal conductivity of the material is.
The thermal conductivity reflects the thermal conductivity of the matter per unit volume, and actually reflects the inherent thermal conductivity of the matter. Thermal resistance is the combination of thermal conductivity and the geometry of the object and reflects the thermal conductivity of the shaped object. The thermal resistance between any two points may be different for an object with non-uniform thickness. Therefore, in terms of a certain matter, it is not meaningful to discuss the thermal resistance. Only when the geometric shape is determined, the concept of thermal resistance can be used to compare the thermal conductivity.
Formula for the relationship between the thermal conductivity and the thermal resistance:
Thermal resistance value R = thickness / thermal conductivity λ
Where R represents the thermal resistance and λ represents the thermal conductivity. It can be seen from this formula that the greater the thermal conductivity, the smaller the thermal resistance, the better the thermal conductivity of the material; otherwise, the smaller the thermal conductivity, the greater the thermal resistance, the worse the thermal conductivity of the material.
EN 12667 / ASTM C518 / GB / T 10295 thermal conductivity test sample size:
300mm * 300mm * thickness
EN 12667 Thermal conductivity test range:
This standard stipulates that the thermal resistance is not less than 0.5 m by protective heat plate or heat flow meter method2Principles and test procedure of sample thermal resistance of.K / W.
I SO 8301:1991 heat flow meter method, the national standard can refer to GB / T 10295-2008
I SO 8302:1991 protective hot plate method, the national standard can refer to GB / T 10294-2008
ASTM C518 Thermal conductivity test range:
This standard is applicable to flat materials with a wide range of measuring thickness and conductivity, and the device adopts heat flow meter device.
The GB / T 10295 thermal conductivity test range
This standard specifies the method for determining the steady-state heat transfer properties of the plate specimens with the applicable heat flowmeter device and the calculation of the heat transfer properties.
Thermal conductivity test —— Thermal flowmeter device principle:
When the heat plate and cold plate are at constant temperature and constant temperature difference, the heat flow meter and the central measuring area of the heat flowmeter establish a unidirectional stable heat flow density through the measuring area of one (or two) heat flowmeter and the middle area of one (or two nearly the same) specimen.
Standard reading for the thermal conductivity test
EN12667 https://www.firete.com/popular_standards/13736.html
ASTM C518 https://www.firete.com/news/zixun/9107.html
GB/T 10295 http://www.hksmartps.com/ce/other/5152.html
ASTM E1530 https://www.firete.com/tr/popular_standards/17080.html
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