Measuring Thermal Conductivity: Methods, Instruments, and Application Ranges

Thermal conductivity (or thermal resistance) is a primary thermal property of insulation materials and a key indicator of their performance. With increasing emphasis on building energy efficiency, accurately determining thermal conductivity is essential for proper material selection. In practice, measurement assesses how a sample’s heat transfer behavior (solid, liquid, or powder) varies with temperature. Common instrument options and temperature ranges include: Laser Flash Analyzer (LFA): -100 to 2000 ℃; Heat Flow Method Analyzer DRL-II: -20 to 300 ℃; Guarded Hot Plate Analyzer DRH-II: -20 to 99 ℃; DRX-II method: 0 to 1300 ℃. 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. Specific heat can also be measured to calculate thermal conductivity. This approach is fast and convenient, and is well-suited to dense materials such as metals and alloys, diamond, ceramics, graphite, and polymer materials. 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 excellent 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 to 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 ensure uniform heat flow. It can test thermal conductivity of refractory insulation materials, ceramic fibers, felts, textiles, boards, and bricks at temperatures up to 1200 ℃. Different materials and service conditions call for different measurement techniques. Selecting an appropriate method based on material structure, temperature range, and sample form ensures reliable thermal conductivity data for design and quality assurance.

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