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Thermal conductivity and diffusivity are the most important thermophysical material parameters for the description of the heat transport properties of a material or component. For the precise measurement of thermophysical properties like the thermal diffusivity, the Laser Flash technique (LFA) has proven itself as a fast, versatile and precise absolute method. NETZSCH offers four LFA models, covering the entire spectrum of materials and temperatures.
Based on an absolute measurement method, the GHP 456 Titan is the ideal instrument for the determination of thermal conductivity of insulations.
The thermal conductivity as another significant thermophysical property is determined by means of heat flow meters (HFM) with the plate method for insulators.
NETZSCH instruments are based on the respective instrument and application standards for LFA (e.g., ASTM E1461, DIN EN 821, BS EN 1159-2, ASTM C714, etc.), for HFM (e.g. ASTM C518, ISO 8301, DIN EN 12667 EN 12, JIS A 1412, based on DIN EN 12664) and for GHP (ISO 8302, ASTM C177, DIN EN 12939, DIN EN 12667, DIN EN 13163)
EnquiryFor the precise measurement of thermal diffusivity a or conductivity (λ), the flash method has established itself as a rapid, versatile and precise measuring method. NETZSCH offers a total of four models (LFA 467 HyperFlash®, LFA 457 MicroFlash®, LFA 467 HyperFlash® HT and LFA 427), which cover the total a broad spectrum of materials and temperature ranges.
The thermal conductivity (λ) of insulation materials can be determined directly with plate instrumentation (HFM = Heat Flow Meter or GHP = Guarded Hot Plate): Included here are the HFM 446 Lambda with its new, expanded measurement capabilities and the GHP 456 Titan® guarded hot plate, which is an absolute method and thus requires no calibration. The instruments listed above operate in accordance with relevant instrument and usage norms. Specifically, these include:
Thermal conductivity (λ with the unit W/(m•K)) describes the transport of energy – in the form of heat – through a body of mass as the result of a temperature gradient (see fig. 1). According to the second law of thermodynamics, heat always flows in the direction of the lower temperature.
The relationship between transported heat per unit of time (dQ/dt or heat flow Q) and the temperature gradient (ΔT/Δx) through Area A (the area through which the heat is flowing perpendicularly at a steady rate) is described by the thermal conductivity equation.
Thermal conductivity is thus a material-specific property used for characterizing steady heat transport. It can be calculated using the following equation:
Where a: Thermal diffusivity
cp: Specific heat capacity
ρ: Density
Thermal diffusivity (a with the unit mm2/s) is a material-specific property for characterizing unsteady heat conduction. This value describes how quickly a material reacts to a change in temperature.
In order to predict cooling processes or to simulate temperature fields, the thermal diffusivity must be known; it is a requisite for solving the Fourier Differential Equation for unsteady heat conduction.
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