Dear colleagues, the core working principle of the thermal conductivity tester for insulation materials is "steady-state heat flow control+precise parameter measurement". It is specifically designed for the low thermal conductivity characteristics of insulation materials to ensure that the test data meets core standards such as GB/T 10294-2008. The specific principle is as follows:

The core of the instrument adopts the protective hot plate method or heat flux meter method, with the commonly used method being the protective hot plate method, which essentially constructs a stable one-dimensional thermal flow field. During testing, the insulation material sample is tightly clamped between the measuring hot plate and the cold plate, surrounded by a protective hot plate. The temperature of the protective hot plate is kept consistent with that of the measuring hot plate (temperature difference ≤ 0.1 ℃), eliminating lateral heat dissipation and allowing heat to only be conducted vertically through the sample.

To eliminate air convection interference, some high-precision instruments will be equipped with vacuum chambers, which will pump the air pressure inside the chamber to the level of 10 ⁻³~10 ⁻⁴ Pa to avoid the influence of air thermal conductivity on the test results of low thermal conductivity materials. Subsequently, test parameters were set, with the hot plate maintained at a constant temperature (adjustable from 50~85 ℃) through electric heating, and the cold plate maintained at a low temperature through a refrigeration system, creating a stable temperature difference (Δ T) of 20~50 ℃ on both sides of the sample.

When the system reaches thermal steady state - the judgment criterion is that the continuous 30 minute heat flux fluctuation is ≤± 1%. The instrument measures the heating power (Q) of the metering hot plate through a high-precision power sensor, and records the effective heat transfer area (A) and thickness (d) of the sample. According to Fourier's law of heat conduction, the thermal conductivity (λ) is automatically calculated using the formula λ=Q × d/(A × Δ T).

Due to the porous and low thermal conductivity characteristics of insulation materials, high requirements are placed on the selection of sensors for instruments: the accuracy of temperature sensors should reach ± 0.05 ℃, and the full-scale error of power sensors should be ≤ ± 1%, ensuring that small changes in heat flux can be accurately captured. Before testing, the sample needs to be pre treated in an environment of 23 ± 2 ℃ and 50 ± 5% RH for at least 72 hours to avoid moisture content affecting the results.

This principle design can accurately adapt to various thermal insulation materials such as rock wool, vacuum insulation board, polyurethane foam, and the test accuracy can be ≤ 1%,satisfyEngineering acceptance, product quality control, and scientific research experimentsreliableData requirements.