Two-color pyrometry for low amplitude periodic heating

Area of Science:

• Materials Science
• Thermodynamics
• Optical Measurement

Background:

• Accurate thermal conductivity measurements are crucial for materials science.
• Periodic heating introduces temperature fluctuations that complicate standard thermal property assessments.
• Extending thermal diffusivity measurements to determine thermal conductivity requires precise temperature probing.

Purpose of the Study:

• To develop and validate a pyrometric method for measuring temperature offset and harmonic amplitudes during periodic heating.
• To extend the application of standard thermal diffusivity measurements for enhanced thermal conductivity determination.
• To provide accurate temperature measurements for specimens subjected to periodic thermal loads.

Main Methods:

• A variation of two-color pyrometry was developed to capture temperature fluctuations.
• Pyrometric formulae were derived using nonlinear thermal emission expansion for low-amplitude heating.
• Experimental uncertainties from radiometric measurements were used to determine temperature uncertainties.

Main Results:

• The developed technique successfully measures both offset and harmonic amplitudes of temperature fluctuations.
• The method demonstrates high accuracy, with uncertainties better than 2% for temperature offset.
• Fluctuating temperature amplitudes were measured with uncertainties ranging from 3% to 8%.

Conclusions:

• The novel two-color pyrometry offers a reliable method for probing temperature responses under periodic heating.
• This technique improves the accuracy of thermal conductivity measurements derived from thermal diffusivity data.
• The validated approach provides well-defined uncertainties, crucial for precise material characterization.