Definition and test methods of thermal conductivity meter

Thermal conductivity meter, referred to as "thermal conductivity meter", is an instrument that measures the thermal conductivity of a sample (solid, liquid or powder) as a function of temperature. At present, there is no unified thermal conductivity testing standard for thermal conductivity measuring instruments. Since the testing methods are different under different standards, choosing a suitable testing method will have a great difference in the measured thermal conductivity. So, what are the current testing methods for thermal conductivity measuring instruments?

Comparison of test methods of DZDR-S thermal conductivity meter

Test method 1. Steady-state method
The steady-state method is a classic method for measuring the thermal conductivity of thermal insulation materials, and it is still widely used today. The principle is to use the equilibrium state in which the heat transfer rate is equal to the heat dissipation rate during the stable heat transfer process. According to the Fourier one-dimensional steady-state heat conduction model, the thermal conductivity is calculated from the heat flux density, temperature difference and thickness of the sample on both sides. The principle is simple and clear, and the accuracy is high, but the measurement time is long and the requirements for environmental conditions are high. The steady-state method is suitable for thermal conductivity materials measured at moderate temperatures. Suitable for low thermal conductivity materials such as rock, plastic, rubber, glass, and thermal insulation materials.

Test method 2. Heat flow method
The heat flow method is a comparative method, which uses a calibrated heat flow sensor to measure the heat flow through the sample and obtains the absolute value of the thermal conductivity. During measurement, a sample with uniform thickness is inserted between two flat plates and a certain temperature gradient is set. The heat flow through the sample is measured using a calibrated heat flow sensor that is in contact with the sample between the plate and the sample.

Test method 3. Transient method (unsteady state method)
The transient method is a thermal conductivity measurement method developed in recent decades. It is used to study materials with medium and high thermal conductivity, or to measure under high temperature conditions. The characteristics of the transient method are fast measurement speed, wide measurement range (up to 2000°C), and simple sample preparation. The working principle is: provide a sample - a heat source with a fixed power, record the temperature changes of the sample itself with time, and obtain the thermal conductivity coefficient, thermal diffusion coefficient and heat capacity of the sample based on the relationship between time and temperature changes. The transient method is suitable for measuring materials with high thermal conductivity or measurements under high temperature conditions. Suitable for homogeneous materials such as metals, graphene, alloys, ceramics, powders, fibers, etc.

DZDR-S thermal conductivity measuring instrument

At present, the measurement methods of thermal conductivity are divided into two categories: steady-state method and transient method (also called unsteady-state method). The above mainly introduces the main test methods in the two major categories of test methods in detail. In fact, the tests for different material applications are different. Therefore, before purchasing a thermal conductivity tester, you must have a certain understanding of its basic test methods, and According to the material being tested, selecting the appropriate testing method for testing can ensure the accuracy of the thermal conductivity measurement results. And the use of the instrument must be based on regular operations to reduce measurement errors.