What is a high-temperature material thermal conductivity tester?

The high-temperature thermal conductivity tester, also known as a high-temperature thermal conductivity meter, is a specialized instrument for measuring the thermal conductivity of refractory insulation materials, ceramic fiber products, boards, and other materials at different temperatures. It is suitable for testing the thermal conductivity of refractory insulation materials, ceramic fibers, felts, textiles, boards, bricks, and similar materials under various temperature conditions. This instrument is widely used in universities, research institutes, quality inspection departments, and manufacturing enterprises for material analysis and testing.

Working Principle

The testing principles of high-temperature thermal conductivity testers are mainly divided into steady-state methods and transient methods, as described below:

Steady-State Methods

Guarded Hot Plate Method:

Based on Fourier’s law of heat conduction, a heated plate is placed between two identical test specimens, with the opposite side of one specimen acting as a cooling surface. Once steady-state conditions are reached (i.e., the temperature distribution within the specimens is stable), the thermal conductivity (k) is calculated using a one-dimensional steady-state heat conduction model:

[q = -k \cdot A \cdot \frac{\Delta T}{\Delta x}]

where (q) is the heat flux, (A) is the heat transfer area, (\Delta T) is the temperature difference across the specimen, and (\Delta x) is the specimen thickness.

Heat Flow Meter Method:

Also based on the steady-state heat conduction equation, this method uses two parallel plates—one heated, one cooled—with the test material placed between them. By measuring the temperatures of the hot and cold plates and the heat flux through the specimen, the thermal conductivity is calculated using the same Fourier formula. High-precision temperature sensors and flow meters are employed to improve measurement accuracy and stability.

Transient Methods

Hot Wire Method:

A heating wire is inserted into the specimen and powered with a known constant current. Based on the wire power and the temperature change measured at two known time intervals after heating, the thermal conductivity is calculated. The method relies on the transient temperature response of a step-heated wire in an infinite medium, using a mathematical model to determine the material’s thermal conductivity.

Laser Flash Method:

A pulsed laser is used to heat one side of the specimen, causing its surface temperature to rise instantly. The heat diffuses through the specimen, and the temperature change on the opposite side is measured over time. Using the thermal diffusion equation and relevant parameters, the thermal diffusivity is calculated. Combined with the material’s density and specific heat capacity, the thermal conductivity is then obtained.

Transient Plane Source (TPS) Method:

A planar probe made of resistive material functions both as a heat source and a temperature sensor. When current passes through the probe, a certain temperature rise occurs, and heat simultaneously diffuses into the specimen on both sides. By recording the temperature response of the probe and applying a mathematical model, the thermal conductivity and thermal diffusivity of the material can be determined directly.

Product Features

Dual Calibration: Simultaneous calibration of temperature and system errors.

Measurement Range: 0.02–5.00 W/(m·K)

Applicable Materials: Refractory insulation, ceramic fibers, felts, textiles, boards, bricks, etc.

Supported Principles: Guarded hot plate method or heat flow meter method.

Control System: Integrated design with PLC and temperature expansion modules.

Output: Uses contactless switching devices.

Control Method: PID control with software-based auto-tuning.

Software: Industrial control software developed in Visual Basic 6.0. supporting real-time data storage, resume from breakpoint, and remote maintenance.

Communication and Storage: RS-232C serial communication, synchronized experimental data collection, and Excel-compatible storage.

Remote Service: Online remote service for maintenance, troubleshooting, and software upgrades.

Operation Procedures

Experimental Preparation

Specimen Preparation:

Prepare two identical specimens; standard size is 300×300×(5–45) mm. Ensure specimens are dry before testing. Loose or soft specimens should be prepared according to GB10294-2008.

Instrument Preparation:

Fill the constant-temperature water bath with distilled or purified water to the full mark. If unused for long periods, drain and dry the bath.

Connect the main unit signal lines to the computer. Insert power and turn on the main switch at the back of the instrument.

Place the furnace horizontally and secure with fixing pins.

Rotate the screw handle to the lowest position, set the thickness gauge to minimum, turn on and zero it, then return the screw to the highest position.

Open the furnace lid and place the first specimen, ensuring full contact with the hot plate. Avoid placing on surrounding fixture materials to prevent air gaps. Close the lid and lock. The pressure module reading must not exceed 2.50; soft specimens should not be over-compressed. Record the thickness gauge reading.

Install the second specimen using the same procedure. Return the furnace to a vertical position for testing.

Experimental Steps

Turn on the water bath: power, circulation, and cooling switches, and set the cold plate temperature.

Launch the computer software and enter the main interface of the thermal conductivity tester. Enter unit, operator, and specimen information.

Set the hot plate temperature.

Use the average of two thickness measurements as the specimen thickness. Preheat for 30 minutes; test duration is typically 150 minutes.

Click “Start Experiment.” After completion, the system automatically generates the test report, which can be saved or printed.

Close the experiment: turn off cooling, circulation, and power switches in sequence. Remove specimens, replace protective boards, and return the equipment to its position.

Clean and cover the instrument; ensure all power is off before leaving the lab.

Maintenance and Care

Avoid Mechanical Shock: Handle the instrument carefully. Regularly check and tighten all components.

Regular Cleaning: Clean the device with a soft cloth after powering off. Avoid corrosive cleaners. Internal cleaning should be done by professionals to prevent water damage.

Calibration: Regular calibration ensures accurate results. Follow the manual or have professionals perform calibration.

Performance Testing: Periodically test the instrument to detect potential issues early and ensure normal operation.

Electrical System Check: Inspect wires, plugs, and sockets for damage or aging, and replace as needed. Check power supply voltage and adjust if abnormal.

By following the above measures, you can ensure the proper operation of the thermal conductivity tester, extend the service life of the equipment, and guarantee the accuracy of test results.