Measuring Thermal Conductivity: Methods, Instruments, and Application Ranges

Thermal conductivity and thermal resistance are key thermal properties of insulation materials. Measurements assess how heat-transfer behavior in solid, liquid, and powder materials varies with temperature.

Common instrument options and temperature ranges include: Laser Flash Analyzer (LFA): −100 to 2,000 °C; Heat Flow Method Analyzer DRL-II: −20 to 300 °C; Guarded Hot Plate Analyzer DRH-II: −20 to 99 °C; DRX-II method: 0–1,300 °C. Additional solutions include the plate heat-flux method (DRPL) and the water-flow guarded-hot-plate method (DRS-II).

Key method highlights:

1) Laser Flash Method (LFA): A laser pulse heats one side of the specimen and an infrared detector records the rear-face temperature rise to compute thermal diffusivity. Thermal conductivity can be calculated when density and specific heat capacity are available. This approach is used for dense materials such as metals and alloys, diamond, ceramics, graphite, and polymers. However, small specimen size can introduce variability in measured data.

2) Heat Flow Method (DRL-II): Considered a standard method for thermal insulation testing, DRL systems use dual heat-flow sensors with controlled temperature stability. Typical applications include building materials, loose-fill and packing materials, powders, gypsum boards, fiberboards, and rubber.

3) Guarded Hot Plate Method (DRH-II): Measurement range is 0.007–2.0 W/(m·K). Its application scope is similar to the heat flow meter method, but it features larger sample sizes and supports testing of non-uniform specimens by design.

4) DRX-II Multi-Method System: Incorporates techniques such as the cross method, parallel-plate method, and T(R) method. It is applicable to refractories, ceramics, polymers, filled plastics, textiles, and concrete, and is suitable for testing soils and liquids.

5) Plate Heat-Flux Method (DRPL): Uses a heat-flux sensor to determine thermal conductivity and thermal resistance. A stable hot-side temperature is applied to one face of the specimen; heat transfer through to the cold side is measured to compute properties. It is suitable for studies of heat transfer in metal profiles and for testing plastics, rubber, graphite, and insulation materials.

6) Water-Flow Guarded-Hot-Plate Method (DRS-II): Employs a centrally guarded calorimeter with external protection and a water-circulation system to maintain uniform heat flow. It can test thermal conductivity of refractory insulation materials, ceramic fibers, felts, textiles, boards, and bricks at temperatures up to 1,200 °C.

Different materials and service conditions call for different measurement techniques. Method selection depends on material structure, temperature range, and specimen form for design and quality-assurance testing.